Since yohimbine strongly stimulates sexual motivation/arousal in rats, it was of interest to determine whether the arousal deficit in aging male rats could be reversed by yohimbine. Three groups from each of two ages (approximately 3 and 15 months) received vehicle, 1 or 4 mg/kg yohimbine. In the mounting test (for arousal/motivation), 1 mg/kg yohimbine significantly increased mount frequency in middle-aged rats, though not to the level of the young animals. In the mating test, the percentage of aging rats intromitting and displaying ejaculatory behavior was less than in the young group, but after 1 mg/kg yohimbine, these behaviors were significantly increased. Vehicle-treated middle-aged rats which had mated showed significantly elevated intercopulatory intervals and ejaculatory behavior latencies. These measures were reduced by 1 mg/kg yohimbine. While behavioral facilitation following yohimbine in aging rats did not reach that of young yohimbine-treated rats, they reached levels at or close to those of nontreated young animals. We conclude that yohimbine treatment can improve age-related deficits seen to occur in aging male rat sexual behavior.