A retrospective review of 552 patients with clinical stage I primary cutaneous malignant melanomas was undertaken comparing margins of resection and local recurrence between 1966 and 1981. The overall local recurrence rate was 8 per 552 (1.45 percent). We observed no instances of local recurrence in lesions less than 1.40 mm thick with resection margins of at least 1 cm. A comparison of resection margins greater than 2 cm versus less than 2 cm for lesions less than 1.00 mm thick showed no difference at the 0.05 level of significance for local recurrence (0 per 228 versus 2 per 154; 1.3 percent) or survival. While narrower margins of resection for thinner, low-risk stage I malignant melanomas appear safe, the exact minimum margin of resection needed to satisfy both oncologic and cosmetic considerations, whether 1 or 2 cm, will need to be determined by a large prospective, randomized study.