OBJECTIVE: Response to erectile dysfunction (ED) treatment has typically been reported over a three-month period in a number of pharmaceutical trials. Little is known about the factors associated with response to treatment over a longer period. The current study examines predictors associated with response to treatment at 12 months in a group of men enrolled in an ED disease registry study. METHODS: Clinical information was collected at baseline and HRQOL data was collected at baseline, 3, 6, and 12-months. Eighty-nine men reported receiving ED treatment while enrolled in the study and completed the 12-month HRQOL questionnaire. Scores on the IIEF erectile functioning scale at baseline and 12-months were compared. Men who reported a 4-point or greater improvement were considered treatment responders (N=40). Forty-nine men were classified as non-responders. A multivariate logistic regression model predicting treatment response at 12 months and controlling for age and baseline erectile functioning was specified. RESULTS: Men who were treatment responders at the 12-month follow-up were significantly more likely at baseline to have a partner who encourages sex (OR=4.230, p=.0369), be unmarried (OR=0.05, p=.0020), report greater rigidity during sex (OR=4.814, p=.0288), and have more frequent morning erections (OR=4.360, p=.0432). CONCLUSIONS: Long-term response to ED treatment is significantly associated with baseline erectile functioning (as measured by frequency of morning erections and penile rigidity during sex) and the supportiveness of a partner. Practitioners can use this information to guide patient expectations for treatment outcomes and to recommend other treatment if relationship concerns are present.