Epiluminescent microscopy is now used frequently for the differential diagnosis of pigmented skin lesions. In order to improve the distinction between benign and malignant melanocytic tumours it seemed advisable to develop a standardized pathway of epiluminescent microscopical analysis and to determine the frequency of structures recognizable with the microscope. A total of 600 melanocytic lesions were examined by epiluminescent microscopy, photographed and classified histologically after excision, revealing 426 naevocellular naevi and 174 melanoma. The experience achieved during the course of the investigation was used as the basis of a procedure for stepwise analysis of keratin layer, pigment structures and blood vessels. The most important findings are described and referred to malignancy. The photographs were analysed for the frequency of occurrence of various pigment structures in different types of lesions. The results differ in several aspects from previous findings.