The aim of the present study was to evaluate the efficacy of sildenafil citrate and its effects on quality of life (QoL) in men with erectile dysfunction (ED) using data from three multicenter, double-blind, placebo-controlled clinical trials. Efficacy was evaluated using a global efficacy question (improvement of erections) and questions from the International Index of Erectile Function (IIEF) addressing the ability to achieve and maintain erections. QoL directly related to ED was evaluated using questions 13 and 14 of the IIEF, several psychometric instruments, and a questionnaire addressing men's concerns about their erection problems. Seventy-nine [corrected] percent of patients receiving sildenafil reported improved erections compared with 23% of patients receiving placebo (p < 0.0001); also reported were improvements in the ability to achieve and maintain erections with sildenafil but not with placebo (p < 0.0001). Improvements were also seen for other aspects of sexual function (overall satisfaction with sex life, sexual relationships with partners, concerns about erectile problems, p < 0.0001) and general mental health (well-being, self-control, satisfaction with relationship, health relative to 1 year ago, mental health; p < or = 0.05) following treatment with sildenafil. Thus, treatment of ED with sildenafil can significantly improve key QoL parameters related to sexual dysfunction and general mental health.