A stepwise schema for the developmental biology of malignant melanomas has been proposed. In this study, two properties associated with malignant transformation— AgNOR production and Ki-67 immunoreactivity—were tested on a series of lesions representative of this model. Fourteen ordinary nevi (N). seven dysplastic nevi (DN), 12 radial growth phase melanomas (RGPM). and eight vertical growth phase melanomas (VGPM) were stained for AgNORs; Ki-67 immunoreactivity was determined in paraffin sections after antigen retrieval. AgNORs averaged 2.1 in N. 3.8 in DN. 5.4 in RGPM. and 7.3 in VGPM (p < 0.001 between all groups). Ki-67 immunoreactivity averaged