OBJECTIVE: To determine if Viagra was more cost-effective than Muse in the treatment of male erectile dysfunction. METHODS: Data on the efficacy of the two drugs was obtained from previous studies on these drugs. Our study period was set at six months. The study patients were males aged between 18-75 years, were in a stable relationship with a female partner for at least six months and were diagnosed with erectile dysfunction for six months or longer. The patients received either Viagra or Muse for treatment of their erectile dysfunction. The study was performed from a payer’s perspective and hence only included cost of the drug and related hospitalizations. Data were also derived from clinicians about the probability of complications, and from some hospitals to obtain the costs of hospitalizations and emergency room visits. The effectiveness measure in our study was the percentage of successful intercourse at the end of the six month period. RESULTS: The percentage of successful intercourse with Viagra treatment was 72% while with the Muse treatment, it was 63%. The incremental cost effectiveness ratio was calculated to be $628 per successful intercourse. CONCLUSION: Our results indicate that one additional successful intercourse would cost $628 more when switching from Muse to Viagra. If using an average cut-off ratio of $50 per successful event which was estimated directly from a group of patients’ preferences as a willingness-to-pay measure, we concluded that Viagra could not be considered to be cost-effective compared to Muse, in the treatment of male erectile dysfunction.