Diabetes mellitus (DM) and erectile dysfunction (ED) are common health problems that markedly increase in prevalence and incidence with advancing age. DM is a known risk factor for developing ED; however, among men with ED it is unknown if DM alters the need for more invasive therapies. We sought to determine whether DM is associated with increased ED severity, reduced effectiveness of first-line (oral) therapies, and therefore higher utilization of second- and third-line therapies. The Inovus I3 database was queried to identify men with ED. Claims were followed for 48 months. Men with incomplete follow-up data and those diagnosed with DM after ED diagnosis were excluded from analysis. Rates of second-line (penile suppositories or injectables) and third-line (penile prostheses) ED therapies were compared between men with and without preexisting DM. Risk of progressing to second- and third-line therapies associated with DM was assessed with logistic regression and Kaplan-Meier analysis. From 1 January 2002 to 31 December 2006, 136 306 men were identified with prevalent and incident ED. Among this group, 19 236 men had DM that preceded their ED diagnosis. Men with DM were more than 50% more likely to be prescribed secondary ED treatments over the 2-year observation period, and more than twice as likely to undergo penile prosthesis surgery. Among a large population-based cohort of men with ED, those with DM are more likely to require more aggressive treatments. These data suggest that ED among men with diabetes may be less responsive to first-line treatments (oral agents), worsen more rapidly, or both.