Sildenafil is being used by a number of patients with erectile dysfunction. Some of these patients also may have concomitant COPD. The effect of sildenafil on lung function is not known. Two patients with severe COPD and erectile dysfunction reported that their dyspnea improved when they took oral sildenafil for erectile dysfunction. Spirometry performed in these patients revealed an improvement in FEV(1) by 24% and 12%. This suggests that, in COPD patients, oral sildenafil does not have any deleterious effect on pulmonary function, and in some patients it may produce a modest improvement in FEV(1).