diff --git a/dotbot/cli.py b/dotbot/cli.py
index 28485d1..c68850c 100644
--- a/dotbot/cli.py
+++ b/dotbot/cli.py
@@ -120,7 +120,8 @@ def main():
 
         plugin_directories = list(options.plugin_dirs)
         if not options.disable_built_in_plugins:
-            from .plugins import Clean, Create, Link, Shell
+            from .plugins import Clean, Create, Link, Shell, Conditional
+            from .conditions import ShellCondition, TtyCondition
         plugin_paths = []
         for directory in plugin_directories:
             for plugin_path in glob.glob(os.path.join(directory, "*.py")):
diff --git a/dotbot/condition.py b/dotbot/condition.py
new file mode 100644
index 0000000..17fcdfc
--- /dev/null
+++ b/dotbot/condition.py
@@ -0,0 +1,27 @@
+import dotbot
+import dotbot.util
+
+from .messenger import Messenger
+
+class Condition(object):
+
+    """
+    Abstract base class for conditions that test whether dotbot should execute tasks/actions
+    """
+
+    def __init__(self, context):
+        self._context = context
+        self._log = Messenger()
+
+    def can_handle(self, directive):
+        """
+        Returns true if the Condition can handle the directive.
+        """
+        raise NotImplementedError
+
+    def handle(self, directive, data):
+        """
+        Executes the test.
+        Returns the boolean value returned by the test
+        """
+        raise NotImplementedError
diff --git a/dotbot/conditions/__init__.py b/dotbot/conditions/__init__.py
new file mode 100644
index 0000000..edeba1d
--- /dev/null
+++ b/dotbot/conditions/__init__.py
@@ -0,0 +1,2 @@
+from .shell import ShellCondition
+from .tty import TtyCondition
diff --git a/dotbot/conditions/shell.py b/dotbot/conditions/shell.py
new file mode 100644
index 0000000..85dedf0
--- /dev/null
+++ b/dotbot/conditions/shell.py
@@ -0,0 +1,20 @@
+from ..condition import Condition
+import dotbot.util
+
+class ShellCondition(Condition):
+
+    """
+    Condition testing an arbitrary shell command and evaluating to true if the return code is zero
+    """
+
+    _directive = "shell"
+
+    def can_handle(self, directive):
+        return directive == self._directive
+
+    def handle(self, directive, command):
+        if directive != self._directive:
+            raise ValueError("ShellCondition cannot handle directive %s" % directive)
+
+        ret = dotbot.util.shell_command(command, cwd=self._context.base_directory())
+        return ret == 0
diff --git a/dotbot/conditions/tty.py b/dotbot/conditions/tty.py
new file mode 100644
index 0000000..ba3539c
--- /dev/null
+++ b/dotbot/conditions/tty.py
@@ -0,0 +1,20 @@
+from ..condition import Condition
+
+import sys
+
+class TtyCondition(Condition):
+
+    """
+    Condition testing if stdin is a TTY (allowing to request input from the user)
+    """
+
+    _directive = "tty"
+
+    def can_handle(self, directive):
+        return directive == self._directive
+
+    def handle(self, directive, data=True):
+        if directive != self._directive:
+            raise ValueError("Tty cannot handle directive %s" % directive)
+        expected = data if data is not None else True
+        return expected == (sys.stdin.isatty() and sys.stdout.isatty() and sys.stderr.isatty())
diff --git a/dotbot/context.py b/dotbot/context.py
index da10ba4..ab140e8 100644
--- a/dotbot/context.py
+++ b/dotbot/context.py
@@ -8,10 +8,11 @@ class Context(object):
     Contextual data and information for plugins.
     """
 
-    def __init__(self, base_directory, options=Namespace()):
+    def __init__(self, base_directory, options=Namespace(), dispatcher=None):
         self._base_directory = base_directory
         self._defaults = {}
         self._options = options
+        self._dispatcher = dispatcher
         pass
 
     def set_base_directory(self, base_directory):
diff --git a/dotbot/plugins/__init__.py b/dotbot/plugins/__init__.py
index f75bef5..98e5916 100644
--- a/dotbot/plugins/__init__.py
+++ b/dotbot/plugins/__init__.py
@@ -1,4 +1,5 @@
 from .clean import Clean
+from .conditional import Conditional
 from .create import Create
 from .link import Link
 from .shell import Shell
diff --git a/dotbot/plugins/conditional.py b/dotbot/plugins/conditional.py
new file mode 100644
index 0000000..a6ddd01
--- /dev/null
+++ b/dotbot/plugins/conditional.py
@@ -0,0 +1,43 @@
+import dotbot
+from dotbot.dispatcher import Dispatcher
+from dotbot.tester import Tester
+
+class Conditional(dotbot.Plugin):
+
+    '''
+    Conditionally execute nested commands based on the result of configured test(s)
+    '''
+
+    _directive = "conditional"
+
+    def can_handle(self, directive):
+        return directive == self._directive
+
+    def handle(self, directive, data):
+        if directive != self._directive:
+            raise ValueError("Conditional cannot handle directive %s" % directive)
+        return self._process_conditional(data)
+
+    def _process_conditional(self, data):
+        success = True
+        tests = data.get("if")
+        test_result = Tester(self._context).evaluate(tests)
+
+        tasks = data.get("then") if test_result else data.get("else")
+        self._log.info("executing sub-commands")
+        # TODO prepend/extract defaults if scope_defaults is False
+        if tasks is not None:
+            return self._execute_tasks(tasks)
+        else:
+            return True
+
+    def _execute_tasks(self, data):
+        # TODO improve handling of defaults either by reusing context/dispatcher -OR- prepend defaults & extract at end
+        dispatcher = Dispatcher(self._context.base_directory(),
+                            only=self._context.options().only,
+                            skip=self._context.options().skip,
+                            options=self._context.options())
+        # if the data is a dictionary, wrap it in a list
+        data = data if type(data) is list else [ data ]
+        return dispatcher.dispatch(data)
+#        return self._context._dispatcher.dispatch(data)
diff --git a/dotbot/tester.py b/dotbot/tester.py
new file mode 100644
index 0000000..3d9928f
--- /dev/null
+++ b/dotbot/tester.py
@@ -0,0 +1,40 @@
+from dotbot.condition import Condition
+from dotbot.messenger import Messenger
+
+class Tester(object):
+
+    def __init__(self, context):
+        self._context = context
+        self._log = Messenger()
+        self.__load_conditions()
+
+    def __load_conditions(self):
+        self._plugins = [plugin(self._context) for plugin in Condition.__subclasses__()]
+
+    def evaluate(self, tests):
+        normalized = self.normalize_tests(tests)
+
+        for task in normalized:
+            for action in task:
+                for plugin in self._plugins:
+                    if plugin.can_handle(action):
+                        try:
+                            local_success = plugin.handle(action, task[action])
+                            if not local_success:
+                                return False
+                        except Exception as err:
+                            self._log.error("An error was encountered while testing condition %s" % action)
+                            self._log.debug(err)
+                            return False
+        return True
+
+    def normalize_tests(self, tests):
+        if isinstance(tests, str):
+            return [ { 'shell': tests } ]
+        elif isinstance(tests, dict):
+            return [ tests ]
+        elif isinstance(tests, list):
+            return map(lambda test: { 'shell': test } if isinstance(test, str) else test, tests)
+        else:
+            # TODO error
+            return []
diff --git a/sample.conf.yaml b/sample.conf.yaml
new file mode 100644
index 0000000..e2a24d1
--- /dev/null
+++ b/sample.conf.yaml
@@ -0,0 +1,26 @@
+- defaults:
+    link:
+      relink: true
+      create: true
+
+- clean: ['~']
+
+- conditional:
+    if:
+      tty: true
+    then:
+      - shell:
+        - 'echo "Running from a TTY"'
+
+- conditional:
+    if:
+      shell: "command -v python"
+    then:
+      - shell:
+        - 'echo "python is available"'
+
+- conditional:
+    if: "command -v foo"
+    else:
+      - shell:
+        - 'echo "foo is not available"'