Aging places men at increased risk for erectile problems, particularly beginning around their fifties and sixties. Using a psychophysiological assessment procedure that included visual erotic stimulation, vibrotactile stimulation, and intracavernosal injection, this study tested for possible age effects on erectile response and self-reported sexual arousal in a group of men clinically diagnosed with erectile dysfunction. We controlled for three factors of purported importance to erectile functioning: existing comorbidities, use of specific medications, and current tobacco and alcohol use. Results indicated effects from both age and tobacco use on erectile response, although these effects were not uniform across age groups. For example, age had inconsistent effects on erectile response in patients aged 50 to 90 years; tobacco use had its strongest effect on patients under 50 years of age. In general, such covariates were less able to account for variation in erectile response among patients with more-severe ED. Despite these effects, ED men even in the oldest group showed average penile circumference increases of 28 mm under JCI, an erectile response typically sufficient for vaginal intercourse. Copyright