The extent and consequence of patient and professional delay in the diagnosis and treatment of 250 consecutive patients with primary cutaneous malignant melanoma was investigated. Mean total delay from the onset of observed change in a melanoma to appropriate therapy was 11.1 months. The major component of delay (9.8 months) was patient related. Seventy-nine (31.6%) patients waited more than 6 months before seeking medical attention. Few patients recognized early melanoma, and 46% responded only to late features (i.e., ulceration or bleeding). Inappropriate professional delay (misdiagnosis or observation without specific action) occurred in 30 consultations (12.4%) and resulted in a further 1.3-month mean delay in treatment. No correlation (r = 0.027) was found between delay in diagnosis and thickness of melanoma for the study population overall. A significant relationship (r = 0.2087; P less than 0.05) was found between longer lag time and advanced disease in 92 patients with nodular melanoma. Asymptomatic melanomas incidentally diagnosed during routine skin surveillance were significantly more favorable (mean depth, 0.89 mm) than symptomatic melanoma (1.76 mm; P less than 0.01). These data suggest that future public education campaigns should emphasize early signs of melanoma and that professional programs should stress routine skin surveillance and prompt referral of suspicious lesions for diagnostic biopsy.