Familial acquired dysplastic nevi carry a risk for the development of melanoma. However, the results in various studies regarding the significance of sporadic dysplastic nevi as a precursor of malignant melanoma (MM), are controversial. The aim of this study is to investigate cyclin D1 expression and Ki67 proliferative index in a group of melanocytic lesions to address the biologic significance of sporadic dysplastic nevi in the progression of melanocytic lesions. Formalin-fixed paraffin-embedded material from 21 common melanocytic nevi, 42 dysplastic nevi, and 17 primary cutaneous MMs were examined. Standard streptavidin-biotin immunoperoxidase method was used for immunostaining with cyclin D1 and Ki-67 antibody. Nuclear cyclin D1 immunostaining was scored and Ki-67 proliferative index was calculated. Cyclin D1 expression was significantly higher in melanoma than those in other lesions. However, there was no significant difference between dysplastic nevi and common melanocytic nevi in terms of cyclin D1 expression. Ki-67 index was significantly higher in dysplastic nevi compared with common melanocytic nevi and to melanoma compared with dysplastic nevi. There was a significant positive correlation between cyclin D1 expression and Ki-67 proliferative index for each group. The present study indicates significant differences in cyclin D1 expressions and Ki-67 indices among melanocytic lesions. We think that dysplastic nevi are biologically separate from common melanocytic nevi in terms of proliferative activity. Additionally, our results suggest that cyclin D1 expression may be related to malignant phenotype and is associated with high proliferation rate in MM.