The extent and consequences of professional delay in diagnosis were analysed in 83 patients with palmoplantar and subungual melanomas treated from January 1986 to March 1997 in our department. Seventeen (52%) out of 33 subungual melanomas and 10 (20%) out of 50 palmoplantar melanomas were clinically misdiagnosed by physicians. Three palmoplantar melanomas (6%) were initially misinterpreted by pathologists. In 23 of the 27 cases (85%) the clinical misdiagnosis was made by non-dermatologists. Misdiagnosis caused a median delay of 12 months in the diagnosis of palmoplantar melanomas and 18 months in the diagnosis of subungual melanomas. Delay in diagnosis was associated with increased tumour thickness, more advanced stage at time of melanoma diagnosis and a lower estimated 5-year survival rate (15.4% versus 68.9% for palmoplantar; 68.5% versus 90.9% for subungual). Acral melanomas are frequently misdiagnosed due to their less common locations and because plantar and subungual melanomas often do not fit the 'changing mole' pattern. To improve the patient's prognosis it is necessary to increase the physicians' skill in the diagnosis of acral melanomas. Histological examination should always be performed in acral lesions that do not heal.