Cortical pyramidal cell development was studied in postnatally lead-exposed kittens by light microscopic and Golgi staining methods. The most evident finding was an elevation of spine density on the distal apical dendritic branches of lead-treated kittens. Also, the branching pattern of the apical dendrites in lead-treated animals was different from control, but there was no overall change in total branch number of the dendritic arbor. Pyramidal cell height and cortical thickness were unaffected. No evidence of vascular damage or other pathologies were found in hematoxylin and eosin-stained sections. The results are discussed with reference to dendritic spine development and function and to other reports of hyperspiny dendrites. Evidence of hyperspiny dendrites in the present study indicates this represents a useful protocol for investigating dendritic spine development and differentiation.