diff --git a/nimble.nimble b/nimble.nimble
index 3170eb2..a7b6e75 100644
--- a/nimble.nimble
+++ b/nimble.nimble
@@ -12,6 +12,13 @@ srcDir = "src"
 
 requires "nim >= 0.11.2"
 
+before tasks:
+  echo("About to list tasks!")
+  return true
+
+after tasks:
+  echo("Listed tasks!")
+
 task tests, "Run the Nimble tester!":
   withDir "tests":
     exec "nim c -r tester"
\ No newline at end of file
diff --git a/src/nimble.nim b/src/nimble.nim
index 97e3027..e501b05 100644
--- a/src/nimble.nim
+++ b/src/nimble.nim
@@ -856,12 +856,23 @@ proc listTasks(options: Options) =
   let nimbleFile = findNimbleFile(getCurrentDir(), true)
   nimscriptsupport.listTasks(nimbleFile, options)
 
+proc execHook(options: Options, before: bool): bool =
+  ## Returns whether to continue.
+  result = true
+  let nimbleFile = findNimbleFile(getCurrentDir(), true)
+  # TODO: Optimise this, there are two (three?) calls to readPackageInfo.
+  if nimbleFile.isNimScript(options):
+    let actionName = ($options.action.typ)[6 .. ^1]
+    let res = execHook(nimbleFile, actionName, before, options)
+    result = res.retVal
+
 proc doAction(options: Options) =
   if not existsDir(options.getNimbleDir()):
     createDir(options.getNimbleDir())
   if not existsDir(options.getPkgsDir):
     createDir(options.getPkgsDir)
 
+  if not execHook(options, true): return
   case options.action.typ
   of actionUpdate:
     update(options)
@@ -898,7 +909,6 @@ proc doAction(options: Options) =
   of actionCustom:
     # Custom command. Attempt to call a NimScript task.
     let nimbleFile = findNimbleFile(getCurrentDir(), true)
-    ## TODO: Optimise this, there are two calls to readPackageInfo here.
     if not nimbleFile.isNimScript(options):
       writeHelp()
 
@@ -910,6 +920,8 @@ proc doAction(options: Options) =
     if execResult.command.normalize == "nop":
       echo("WARNING: Using `setCommand 'nop'` is not necessary.")
       return
+    if not execHook(options, false):
+      return
     if execResult.hasTaskRequestedCommand():
       var newOptions = initOptions()
       newOptions.config = options.config
@@ -921,6 +933,9 @@ proc doAction(options: Options) =
         parseFlag(flag, val, newOptions)
       doAction(newOptions)
 
+  if options.action.typ != actionCustom:
+    discard execHook(options, false)
+
 when isMainModule:
   when defined(release):
     try:
diff --git a/src/nimblepkg/nimscriptapi.nim b/src/nimblepkg/nimscriptapi.nim
index c996e1a..af5171d 100644
--- a/src/nimblepkg/nimscriptapi.nim
+++ b/src/nimblepkg/nimscriptapi.nim
@@ -24,6 +24,17 @@ proc requires*(deps: varargs[string]) =
   ## package.
   for d in deps: requiresData.add(d)
 
+template before*(action: untyped, body: untyped): untyped =
+  ## Defines a block of code which is evaluated before ``action`` is executed.
+  proc `action Before`*(): bool =
+    result = false
+    body
+
+template after*(action: untyped, body: untyped): untyped =
+  ## Defines a block of code which is evaluated after ``action`` is executed.
+  proc `action After`*(): bool =
+    body
+
 template builtin = discard
 
 proc getPkgDir*(): string =
diff --git a/src/nimblepkg/nimscriptsupport.nim b/src/nimblepkg/nimscriptsupport.nim
index b74da46..4622c62 100644
--- a/src/nimblepkg/nimscriptsupport.nim
+++ b/src/nimblepkg/nimscriptsupport.nim
@@ -12,18 +12,21 @@ import
 
 from compiler/scriptconfig import setupVM
 from compiler/idents import getIdent
-from compiler/astalgo import strTableGet
+from compiler/astalgo import strTableGet, `$`
 import compiler/options as compiler_options
 
+import compiler/renderer
+
 import nimbletypes, version, options, packageinfo
 import os, strutils, strtabs, times, osproc
 
 type
-  ExecutionResult* = object
+  ExecutionResult*[T] = object
     success*: bool
     command*: string
     arguments*: seq[string]
     flags*: StringTableRef
+    retVal*: T
 
 const
   internalCmd = "NimbleInternal"
@@ -174,18 +177,20 @@ proc setupVM(module: PSym; scriptName: string,
 proc findNimscriptApi(options: Options): string =
   ## Returns the directory containing ``nimscriptapi.nim``
   var inPath = false
-  let pkgs = getInstalledPkgsMin(options.getPkgsDir(), options)
-  var pkg: PackageInfo
-  if pkgs.findPkg(("nimble", newVRAny()), pkg):
-    let pkgDir = pkg.getRealDir()
-    if fileExists(pkgDir / "nimblepkg" / "nimscriptapi.nim"):
-      result = pkgDir
-      inPath = true
+  # Try finding it in exe's path
+  if fileExists(getAppDir() / "nimblepkg" / "nimscriptapi.nim"):
+    result = getAppDir()
+    inPath = true
+
   if not inPath:
-    # Try finding it in exe's path
-    if fileExists(getAppDir() / "nimblepkg" / "nimscriptapi.nim"):
-      result = getAppDir()
-      inPath = true
+    let pkgs = getInstalledPkgsMin(options.getPkgsDir(), options)
+    var pkg: PackageInfo
+    if pkgs.findPkg(("nimble", newVRAny()), pkg):
+      let pkgDir = pkg.getRealDir()
+      if fileExists(pkgDir / "nimblepkg" / "nimscriptapi.nim"):
+        result = pkgDir
+        inPath = true
+
   if not inPath:
     raise newException(NimbleError, "Cannot find nimscriptapi.nim")
 
@@ -196,6 +201,8 @@ proc execScript(scriptName: string, flags: StringTableRef, options: Options) =
   if "nimblepkg/nimscriptapi" notin compiler_options.implicitIncludes:
     compiler_options.implicitIncludes.add("nimblepkg/nimscriptapi")
 
+  let pkgName = scriptName.splitFile.name
+
   # Ensure that "nimblepkg/nimscriptapi" is in the PATH.
   let nimscriptApiPath = findNimscriptApi(options)
   appendStr(searchPaths, nimscriptApiPath)
@@ -219,10 +226,10 @@ proc execScript(scriptName: string, flags: StringTableRef, options: Options) =
 
   # Setup builtins defined in nimscriptapi.nim
   template cbApi(name, body) {.dirty.} =
-    vm.globalCtx.registerCallback "stdlib.system." & astToStr(name),
+    vm.globalCtx.registerCallback pkgName & "." & astToStr(name),
       proc (a: VmArgs) =
         body
-  # TODO: This doesn't work.
+
   cbApi getPkgDir:
     setResult(a, "FOOBAR")
 
@@ -318,7 +325,7 @@ proc readPackageInfoFromNims*(scriptName: string, options: Options,
   cleanup()
 
 proc execTask*(scriptName, taskName: string,
-    options: Options): ExecutionResult =
+    options: Options): ExecutionResult[void] =
   ## Executes the specified task in the specified script.
   ##
   ## `scriptName` should be a filename pointing to the nimscript file.
@@ -347,6 +354,44 @@ proc execTask*(scriptName, taskName: string,
 
   cleanup()
 
+proc execHook*(scriptName, actionName: string, before: bool,
+    options: Options): ExecutionResult[bool] =
+  ## Executes the specified action's hook. Depending on ``before``, either
+  ## the "before" or the "after" hook.
+  ##
+  ## `scriptName` should be a filename pointing to the nimscript file.
+  result.success = true
+  result.flags = newStringTable()
+  compiler_options.command = internalCmd
+  let hookName =
+    if before: actionName.toLower & "Before"
+    else: actionName.toLower & "After"
+  echo("Attempting to execute hook ", hookName, " in ", scriptName)
+
+  execScript(scriptName, result.flags, options)
+  # Explicitly execute the task procedure, instead of relying on hack.
+  let idx = fileInfoIdx(scriptName)
+  let thisModule = getModule(idx)
+  assert thisModule.kind == skModule
+  let prc = thisModule.tab.strTableGet(getIdent(hookName))
+  if prc.isNil:
+    # Procedure not defined in the NimScript module.
+    result.success = false
+    return
+  let returnVal = vm.globalCtx.execProc(prc, [])
+  case returnVal.kind
+  of nkCharLit..nkUInt64Lit:
+    result.retVal = returnVal.intVal == 1
+  else: assert false
+
+  # Read the command, arguments and flags set by the executed task.
+  result.command = compiler_options.command
+  result.arguments = @[]
+  for arg in compiler_options.gProjectName.split():
+    result.arguments.add(arg)
+
+  cleanup()
+
 proc getNimScriptCommand(): string =
   compiler_options.command
 
diff --git a/src/nimblepkg/options.nim b/src/nimblepkg/options.nim
index a7950c0..3af5817 100644
--- a/src/nimblepkg/options.nim
+++ b/src/nimblepkg/options.nim
@@ -29,8 +29,6 @@ type
     of actionUpdate:
       optionalURL*: string # Overrides default package list.
     of actionInstall, actionPath, actionUninstall:
-      optionalName*: seq[string] # \
-      # When this is @[], installs package from current dir.
       packages*: seq[PkgTuple] # Optional only for actionInstall.
     of actionSearch:
       search*: seq[string] # Search string.