Androgen receptor and Ki-67 were immunohistochemically investigated in biopsy specimens taken from 50 cases of prostatic carcinoma and the correlation between histologic grade and AR and Ki-67 was examined using a computer-assisted image analysis system. When the immunoreactive intensity of AR of tumor cells was the same or stronger than that of stromal cells in the same section, the tumor cells were defined AR-positive. An immunohistochemical study revealed that AR positive cases-were significantly higher in well differentiated type (86%) and moderately differentiated type (85%) than in poorly (38%) differentiated type. The expression of Ki-67 was significantly higher in poorly and moderately differentiated types than in well, differentiated type. There was a significant correlation between the histologic grade, and AR and Ki-67; however, there was no correlation between the clinical stage and AR or Ki-67.