GABAergic interneurons perform crucial roles in cortical development and function. These roles are executed by a diversity of interneuron subtypes, and abnormal function of particular subtypes has been implicated in a variety of neuropsychiatric diseases. However, little is known about the mechanisms that generate interneuron diversity. This paper discusses the potential origins of interneuron subtypes. Evidence is reviewed that suggests bipolar calretinin expressing interneurons may have distinct origins from those that express parvalbumin or somatostatin. In addition, evidence is presented that migratory cells from the subcortical subventricular zone (SVZ) do not proliferate after migration into the cortical SVZ.