Retrograde ejaculation (RE) and erectile dysfunction may be caused by diabetes mellitus (DM), but the prevalence of RE among DM patients is unknown. A prospective, blinded case-control study comparing men with DM with matched controls according to RE and erectile dysfunction was performed. Twenty-seven men with DM matched the inclusion criteria and agreed to participate in the study, and of these 26 delivered an ejaculate. We were able to recruit 18 matching controls, and of these 16 delivered an ejaculate. Nine of 26 men with DM who delivered an ejaculate had RE, whereas none of 16 controls had RE (p