Many men with erectile dysfunction (ED) have hypertension as a comorbid condition. Recent guidelines recommend thiazide diuretics as first-line therapy for hypertension. We analyzed data from 14 randomized, double-blind, placebo-controlled trials (N=2501) to evaluate the efficacy of tadalafil 20 mg for the treatment of ED in men on thiazides. Of the 2501 patients, 163 were on concomitant thiazides (116 tadalafil/47 placebo) and 159 (98%) were reported to have hypertension. The primary efficacy measures were mean change from baseline in the international index of erectile function (IIEF) erectile function (EF) domain and the proportion of 'yes' responses to sexual encounter profile (SEP) Questions 2 and 3. The tadalafil group showed a significantly (P<0.001) greater mean baseline to endpoint improvement on all efficacy outcome measures compared to placebo-treated patients regardless of concomitant thiazide use. More importantly, the responses to tadalafil were similar regardless of concomitant thiazide use. Additionally, responses to tadalafil were comparable between thiazide and nonthiazide users regardless of baseline ED severity (P>0.05).