Clinical characteristics of the primary tumor in 786 patients with superficial spreading melanoma were studied in a prospective sequential series of patients from the Melanoma Clinical Cooperative Group. The most useful features for early diagnosis were change in size and change in color, present in 71% and 55% respectively of patients with level II lesions. Increase in height of lesion correlated with more advanced disease. Ulceration and bleeding were predominantly found in advanced primary lesions and are consequently of limited use in early recognition. Awareness of the historical and clinical features of the primary tumor should result in early recognition and cure of most primary superficial spreading melanomas.