OBJECTIVE To study on reproductive and immune toxicity of male rats exposed to subacute As2O3. METHODS 24 male rats of KM-strain were divided into four groups and were given by gavage deionized water, 2.0, 4.0 and 8.0 mg As/(kg x bw) for 7 days. After the exposure, the rats were killed and the testis, epididymis were collected and analysed. RESULTS (1) In comparison with control, testicular and epididymal weights were lower than those of high dose group (P < 0.05), but there were no difference of testicular indexes between exposed group and control. The stained sperm count were lower than those of arsenic exposure group (P > 0.05), and malformation rate of sperm were significant increase in middle- and high-dose group (P < 0.05); (2) Compared to control, the weight and index of immune organ was decrease in middle-and high-dose group, and the spleen weight and index was significantly lower in high-dose group (P < 0.05). CONCLUSIONS As2O3 can induce reproductive and immunotoxicity in male mice.