Objective To investigate the expression of cyclin D3 and proliferating cell nuclear antigen (PCNA) and their clinical significance in mal ignant melanoma. Methods The expression of cyclin D3 and PCNA was measured by streptavidin-peroxidase complex immunohistochemical technique in 57 cases of pri mary cutaneous malignant melanoma (CMM), 37 cases of metastatic melanoma and 20 cases of benign nevi. Results The positive expression rate of cyclin D3 in CM M and metastatic melanoma were 35.1% and 59.5% respectively, while the high expr ession rate of PCNA were 57.9% and 78.6% respectively. Compared with that in ben ign nevi, the expression of cyclin D3 and PCNA was significantly increased. The expression of cyclin D3 and PCNA in CMM was positively related to Clark′s grade and the metastasis to lymph nodes. The 3-year survival rate in patients with ne gative expression of cyclin D3 was significantly higher than that with positive expression in superficial melanomas. The 3-year survival rate of patients with l ow expression of PCNA was significantly higher than that with high expression in CMM. The expression of cyclin D3 was positively correlated with the high expres sion of PCNA in superficial and metastatic melanomas. Conclusions The expressi on of cyclin D3 and PCNA may be involved in the carcinogenesis process and progr ession of CMM and have important implications in the selection of therapeutic re gimens and prognostic assessment. The expression level of cyclin D3 may be regar ded as a prognostic factor for superficial melanoma.