The present study was designed to evaluate the effect of ethanol on pituitary adenylate cyclase activating polypeptide (PACAP) and its typ I (PAC1) receptor expression in adult rat testes. Ethanol (3 g/kg i.p., 15% v/v in saline) was administrated to adult male rats for 10 days. Using northern blot analysis, the present study showed the reduction of PACAP mRNA levels in rat testes by ethanol administration. Also, ethanol decreased the expression level of PAC1 receptor in testes. In particular, in situ hybridization clearly showed the decrease of PAC1 receptor mRNA expression in Leydig cells, which produce testosterone. Furthermore, the serum level of testosterone was significantly decreased in the ethanol-treated group. In conclusion, our findings suggest that the decrease of PACAP and PAC1 receptor expression in rat testes by ethanol exposure may partly contribute to the suppression of male reproductive activity.