Of the numerous problems associated with the pigmented nevi, those concerned with the diagnosis and treatment of the junction nevus and nevocarcinoma (melanoma) are the most important. By the presentation of an orderly concept of junction nevus and nevocarcinoma, it is the purpose of this discussion to provide a working basis for their management. Terminology.— We do not favor the term melanoma, as it is used loosely at times to denote any type of pigmented nevus; and it is ambiguous, as it refers both to a certain type of nevus and to the malignant growth which develops from it. We prefer the terms junction nevus and nevocarcinoma since they are more specific and more descriptive and eliminate the previous objections. Junction nevus is a cellular nevus in which nests of nevus cells can be seen with ease in the basal cell zone. It is called junction because it arises at