The purpose of this study was to establish a morphometric technique that would approximate the subjective histological criteria of asymmetry in the diagnosis of malignant melanoma. The dermal and epidermal outlines of 52 consecutive malignant melanomas and 56 consecutive melanocytic nevi were digitized and analyzed for morphometric parameters of size, coordinates, and shape. The two parameters that showed the most significant discriminatory functions were the differences in the center of masses of the epidermal and dermal components in the horizontal dimension and the length of the longest segment in the lesion.