Using peanut agglutinin(PNA), neurarninidase, and avidin-biotin peroxidase com plex(ABC) technique, normal skin specimens, nevocellular nevi, and malignant melanomas were studied, and different PNA binding patterns between nevocellular nevi and malignant melanomas were observed. The results were as follows : 1. In normal skin, except the basement membrane, epidermis and hair follicle epithelium showed a cell membrane staining of PNA after neuraminidase pretreat ment. Sebaceous glands revealed membranous and cytoplasmic staining of PNA, but sweat ducts were not stained. 2. In nevocellular nevi, none of the nevus cells were stained with PNA aftet neuraminidase preteatment. 3. In malignant melanomas, all of the melanorna cells were stained along the cell mernbrane with PNA after neuraminidase pretreatment. Therefore, the PNA staining after neuraminidase pretreatment on paraffin embedded sections using ABC technique is considered to be a useful probe for the differentiation between malignant malanoma and nevocellular nevus. (Kor J Dermatol 28(3): 315 320, 1990)