: A retrospective review of 118 clinical Stage I melanoma patients, including the re-examination of histologic slides in 57 cases, was performed to define factors important to survival. The majority (76.7%) had excision margins of 30 mm or less (range = 6-85 mm, mean--29.3 mm). The adjusted 5-year survival was 77.3%. Local recurrences within 5 cm of the primary closure scar developed in 3.4%. The recurrences occurred in patients with satellitosis (1), unrecognized subclinical Stage II disease (1), or as the first evidence of disseminated Stage III disease (2). Margins less than 20 mm were associated with an increased risk of dying if the tumor diameter was more than 10 mm (p = 0.0105) or if the depth of invasion was more than 2.0 mm (p = 0.0491). Increasing the margin to 25 mm improved survival. However, no further protection was evident for margins over 30 mm. For smaller and shallower lesions, no optimal margin could be identified. It appears that a 30 mm margin is adequate for large and deep clinical Stage I melanomas, and mortality and local recurrences are due to factors other than the extent of excision.