The arrest-defective-1 (ARD1) gene has been reported to be important in yeast cell cycle regulation, and recent studies have shown that human arrest-defective-1 (hARD1) is related to cancer cell proliferation. To investigate the expression pattern of hARD1 protein in cancer tissues, immunohistochemical analysis was performed to analyze the hARD1 expression pattern in 400 cases of 19 types of common cancer and 133 non-cancer samples from 11 tissue types. hARD1 protein was expressed extensively in cancer tissues including glandular carcinoma and squamous cancer, and the positive rate was 71.5% (15/20) in urinary bladder cancer, 62.5% (30/48) in breast cancer and 57.1% (8/14) in cervical carcinoma. The average hARD1-positive rate was 52.3% in cancers and 31.5% in non-cancers, for which the difference was significant (p<0.005). Comparing the staining intensity of different fields in the same section, the hARD1 protein was highly accumulated in cancer cells when compared to the cells adjacent to cancer. The positive rate of breast and intestinal cancer was obviously higher than corresponding non-cancers (p<0.05 and 0.01). These findings suggest that the accumulation of hARD1 protein may be related to carcinogenesis of various types of cancer.