A coculture of dermal papilla cells (DPCs) from the bald frontal scalp of stumptailed macaques with keratinocytes derived from human neonatal foreskin revealed that testosterone inhibited keratinocyte proliferation, and that the antiandrogen RU58841 abolished this response. This testosterone-induced keratinocyte growth inhibition was not observed when either type of cells was cultured alone. We also examined conditioned media from the coculture system and demonstrated the identical testosterone-induced growth inhibition on keratinocytes, and this inhibitory effect was conditioned media concentration-dependent. These results suggested that the testosterone-mediated suppression on keratinocyte proliferation might proceed through some diffusible growth mediators in conditioned media. Differential display reverse transcriptase polymerase chain reaction allowed us to isolate several genes from frontal DPCs that can be either suppressed or induced by testosterone. Supervillin, a membrane-associated, F-actin-binding protein, was identified as one of the testosterone downregulated genes in frontal DPCs, Further characterization of these testosterone-target genes may reveal the mechanism by which testosterone inhibits the growth of follicular cells in androgenetic alopecia.