The migratory paths of interneurons derived from the ganglionic eminence (GE), and particularly its caudal portion (CGE), remain essentially unknown. To clarify the three-dimensional migration profile of interneurons derived from each part of the GE, we developed a technique involving focal electroporation into a small, defined portion of the telencephalic hemisphere. While the medial GE cells migrated laterally and spread widely throughout the cortex, the majority of the CGE cells migrated caudally toward the caudal-most end of the telencephalon. Time-lapse imaging and an in vivo immunohistochemical study confirmed the existence of a migratory stream depicted by a population of CGE cells directed caudally that eventually reached the hippocampus. Transplantation experiments suggested that the caudal direction of migration of the CGE cells was intrinsically determined as early as embryonic day 13.5. The caudal migratory stream is a novel migratory path for a population of CGE-derived interneurons passing from the subpallium to the hippocampus.