Fifty partial and non-responders (Clinical Global Impression-Sexual Function (CGI-SF) score>2), out of 76 men who completed a 6-week, double-blind, placebo-controlled trial of sildenafil treatment for serotonergic antidepressant-associated sexual dysfunction, were eligible for an additional 6-week trial of open-label sildenafil (50 mg adjustable to 100 mg) under the same protocol, with blind maintained to initial assignment. Participation (double-blind and open-label) required major depressive disorder in remission (MDD-R) and continuing antidepressant medication. Forty-three entered open-label study: 16/17 initially randomized to sildenafil (sildenafil/sildenafil) and 27/33 initially randomized to placebo (placebo/sildenafil). Thirty-five of 43 (81%) achieved full response (CGI-SF<or=2): placebo/sildenafil 23/27 (85%); sildenafil/sildenafil 12/16 (75%); P<0.0001 for changes and P=0.4 between groups. Secondary measures of erectile function and overall satisfaction improved in both groups (P<0.03). Hamilton Depression Rating Scale scores improved (placebo/sildenafil; P<or=0.05) or remained stable (sildenafil/sildenafil). In men with MDD-R who maintained antidepressant adherence, 81% of double-blind partial and non-responders treated with open-label sildenafil responded fully.