Objective: To elucidate the expression and significance of cell cycle protein cyclin D1 in human hepatocellular carcinoma (HCC). Methods: The expression of cyclin D1 protein in 29 cases of HCC tissues was detected by immunohistochemical ABC method, and the relationship between its positive rate and pathological grades of HCC tissues was analyzed. Results: The positive rate of cyclin D1 in HCC tissues was 58.6%(17 in 29 cases), whereas only 18.2% (2 cases of 11 cases) in the non-tumor liver tissues immediately adjacent to HCC tissues (LAH). There was significant difference between grade II and LAH tissues (P<0.05), and between grade I and grade III on the positive rate of cyclin D1 (P<0.05), respectively. Conclusion: Cyclin D1 may be regarded as an oncogenic marker during the genesis and development of HCC, and its role in the transforming process from G1 phase to S phase of HCC cells needs further studies. Objective: To elucidate the expression and significance of cell cycle protein cyclin D1 in human hepatocellular carcinoma (HCC). Methods: The expression of cyclin D1 protein in 29 cases of HCC tissues was detected by immunohistochemical ABC method, and the relationship between its positive rate Results of the positive rate of cyclin D1 in HCC tissues was 58.6% (17 in 29 cases), because only 18.2% (2 cases of 11 cases) in the non-tumor To HCC tissues (LAH). There was significant difference between grade II and LAH tissues (P<0.05), and between grade I and grade III on the positive rate of cyclin D1 (P<0.05), respectively. Conclusion: Cyclin D1 may Be regarded as an oncogenic marker during the genesis and development of HCC, and its role in the transforming process from G1 phase to S phase of HCC cells needs further studies.