We estimated the potential benefit of reducing rates of inadequate excision margins in the treatment of localized invasive melanoma. A computer-simulated Markov decision analytic model was created to follow until death a hypothetical cohort of 55 y old Caucasians, newly diagnosed in a community setting with localized invasive melanoma. We considered two scenarios: usual care, and a hypothetical intervention. Markov states included well without local recurrence, local recurrence, cured, and dead. Published population-based data were used for rates of optimal excision margins, local recurrence, and mortality. Two outcome measures were employed: melanoma-related mortality and life expectancy. Major assumptions included: local recurrence occurs within 10 y of diagnosis, and patients revert to general population mortality rates 10 y following melanoma excision or subsequent local recurrence. For usual care, the model estimated 8.17% melanoma-related mortality. Modeling intervention with 100% optimal excision margins reduced this rate to 6.15%, a 25% relative reduction in mortality. This increased average life expectancy by 0.437 y, which equates to approximately 11 additional years in the 4% who would not experience a local recurrence due to improved excision margins. Increasing the percentage of optimal excision margins to 80% would still yield substantial improvement, with 6.83% melanoma-related mortality, saving 0.29 life-years compared with baseline. Results were insensitive to moderate changes in the parameter values. Suboptimal excision margins may account for approximately one-fourth of all melanoma-related mortality for localized invasive melanoma. If intervention can achieve even modest adherence to optimal excision margins, it might substantially reduce mortality.