In a double-blind, placebo-controlled crossover study on a group of men with erectile problems and a sexually functional comparison group, the effect of yohimbine (up to 30 mg/day) was assessed on a number of objective and subjective measures of erectile response through the use of daily logs and psychophysiological laboratory procedures involving response to visual sexual stimulation (VSS). Sexual desire, arousal, and ejaculatory response were also assessed. Results indicated no effect of yohimbine on most aspects of sexual response in sexually functional men. Mixed effects were found on measures of sexual function in men erectile dysfunction, with 3 of 11 men reporting strong positive effects. Under yohimbine, frequency of sexual activities increased, as did self-assessed genital response to VSS. Daily diaries indicated increased sexual arousal and erectile response during masturbation but not intercourse. A number of other measures, including NPT and retrospective summaries of erectile functioning at the end of drug phases, showed no effect. Results are discussed in terms of possible yohimbic effects on psychological factors that modulate overall sexual response, and consequently, erectile response.