WE FEEL rather privileged to have been asked to participate in a symposium held by dermatologists. We are general pathologists, but it is abundantly clear that many of the key contributions to the understanding of the histologic nature of pigmented tumors have been made by dermatologists, especially by those great and pioneering dermatologists, Unna and Bloch. However, it must also be evident that the problems of nevi and malignant melanomas transcend party lines, as you obviously agree, and it would be well if this example were followed frequently and bilaterally. Certainly, there is no place for professional chauvinism in the interpretation of scientific data. This presentation is concerned, first, with a recapitulation of clinicopathological impressions based on data from a recent study of these lesions at the Memorial Cancer Center3and, secondly, with a fairly detailed ledger and evaluation of the evidence for the major concepts