OBJECTIVE: Clinical trials suggest that sildenafil is an effective treatment for erectile dysfunction. Nevertheless, reimbursement is controversial: sildenafil is expected to be more effective than conservative therapy (papaverine/ phentolamine injections), but also more costly to society. Economic appraisal of sildenafil is of interest given the prevalence of the disorder. DESIGN: We analyzed the cost-effectiveness of a sildenafil scenario (allowing a switch to injection therapy) and the papaverine/ phentolamine scenario (conservative therapy, no switch allowed). Analyses were performed from the societal perspective. Values for health states of erectile dysfunction were collected using time trade-off. Using these values (N=169), we converted trial outcomes (Goldstein, 1998) into quality adjusted life