We analyzed the results at 8 years of an international, randomized, prospective study carried out by the World Health Organization Melanoma Programme aimed at evaluating the efficacy of 1-cm-margin excision of primary melanomas not thicker than 2 mm. Data for 612 patients were assessable; 305 were randomized to receive 1-cm-margin excision and 307 to receive wide excision (margins of greater than or equal to 3 cm). The major prognostic criteria were similar in the two groups. Breslow thickness was 0.99 mm in the narrow excision group and 1.02 mm in the wide excision group. Disease-free and overall survival rates (mean follow-up period, 90 months) were similar in the two groups. Only four patients had a local recurrence as a first relapse. All underwent narrow excision, and each had primary melanomas thicker than 1 mm.