INTRODUCTION AND OBJECTIVE: Transrectal ultrasound biopsy of prostate is a painful procedure. The introduction of the rectal probe is one of the major contributors to the pain associated with this procedure. Drugs that relax the anal sphincter should theoretically decrease this pain. This study was done to compare the efficacy and safety of two topical medications that relax the anal sphincter, diltiazem and nitroglycerine, in decreasing the pain associated with transrectal ultrasound guided prostate biopsy. MATERIALS AND METHODS: 66 patients who were to undergo their first prostate biopsy were randomized to receive either 2 mL of 2% topical diltiazem or 2 mL of 0.2% topical nitroglycerine or placebo 20 minutes before prostate biopsy. All patients also received 15 mL of intrarectal lignocaine. A 10-point visual analogue score was used to record the pain immediately after the insertion of the probe, during biopsy and at the end of the procedure. RESULTS: The pain scores due to probe insertion, during biopsy and at the end of the procedure in patients who received topical diltiazem or nitroglycerine were significantly lower compared to the placebo group (p < 0.001). There were no significant differences in the pain scores between the patients receiving diltiazem compared to those receiving nitroglycerine. Higher incidence of headache and fall in blood pressure was noted in patients who received nitroglycerine compared to those receiving diltiazem. CONCLUSION:Topical diltiazem and nitroglycerine are equally effective in reducing the pain associated with transrectal prostatic biopsy. Diltiazem is safer compared to nitroglycerine.