PURPOSE: To assess the effectiveness and clinical usefulness of prostate biopsy by automated gun biopsy device under the transrectal ultrasonographic guidance, authors analysed the result of biopsy and the patients status after biopsy procedure. METHODS AND MATERIALS: The subjects consisted of 24 patients with prostatic disease. Biopsy instrument was an automated gun biopsy device loaded with an 18 gauze biopsy needle. All the patients were admitted to the hospital. No analgesics was given. All the procedure was performed with the patient in left lateral decubitus. Biopsy was performed at 2-4 different points of the prostate in 22 cases, but recently, six different points were targeted in two patients. RESULTS: Biopsy specimens were sufficient in 21 cases but insufficient in three cases. Histologic examination of biopsy specimens showed that 13 cases were nodular hyperplasia, eight cases were cancerous and three cases were inflammation. There was no clinically significant complication. There was mild to moderate degree of pain in all patients. CONCLUSION: Tansrectal biopsy of the prostate with an automated gun biopsy device under ultrasonographic guidance is considered relatively easy, handy and useful procedure in patients with prostatic disease. The procedure may be performed on the outpatient basis.