The rate of kindling of a primary site in the dorsal hippocampus of rats was not altered by various forebrain commissurotomies or midbrain bisection. The positive transfer in the kindling of a secondary site in the homotopic hippocampus, on the other hand, was abolished by extensive forebrain transection, whereas anterior callosal or midbrain bisection alone was ineffective. In addition, there was no evidence of an interference effect when rekindling the original primary site. These results have important implications for interhemispheric mechanisms in kindling.