BACKGROUND Currently, there are relatively few studies on the effects of changes in oestrogen and androgen levels on prostatic microvessel density (MVD). This article aimed to study the changes in prostatic MVD in Sprague-Dawley (SD) rats after castration under the effect of oestrogen/androgen at different concentrations. METHODS Male SD rats aged 3-4 months were randomly divided into a control group, a castration group, and groups with different concentrations of oestrogen/androgen treatment after castration. Dihydrotestosterone (DHT) and oestradiol (E) were administered daily by subcutaneous injection for one month. All the rats were killed by cervical dislocation after one month, and the serum DHT and E concentrations of the rats in each group were measured by ELISA. Prostate tissue specimens were immunohistochemically stained with monoclonal antibodies against CD34 and factor VIII for MVD. RESULTS Compared with the control group, the MVD decreased significantly in the castration group (P < 0.05). When the exogenous E concentration was constant, in general, the MVD of rats in all the groups increased with increasing exogenous DHT concentration. Compared with the castration group, the MVD increased significantly in the E0.05 + DHT0.015 mg/kg, E0.05 + DHT0.05 mg/kg, E0.05 + DHT0.15 mg/kg, E0.05 + DHT0.5 mg/kg, and E0.05 + DHT1.5 mg/kg groups (P < 0.05). In addition, when the exogenous DHT concentration was constant, the MVD increased with increasing exogenous E concentration in all the groups. Among them, compared with the control and castration groups, the MVD increased significantly in the DHT0.15 + E0.015 mg/kg, DHT0.15 + E0.15 mg/kg, and DHT0.15 + E0.5 mg/kg groups (P < 0.05). CONCLUSIONS Androgens play an important role in the regulation of prostatic MVD in SD rats, and a decrease in DHT concentration can induce a decrease in prostatic MVD. In contrast, prostatic MVD can be increased with increasing DHT concentration. In addition, prostatic MVD can be increased gradually with increasing oestrogen concentration.