To examine the frequency and severity of toxicity associated with flutamide inpatients treated with total androgen suppression before and during pelvic radiation therapy (RT) for prostate cancer. Sixty-five patients with T2b-T4 prostate cancer received flutamide and goserelin acetate for 4 months, with RT beginning at the 3rd month. Treatment records including liver function test (LFT) results at baseline and during treatment were reviewed and toxicities noted. In 30 (46%) of 65 patients, flutamide was discontinued prematurely. Primary reasons included elevation in LFT levels (n=14); gastro-intestinal toxicity (n=9); decreased hemoglobin level (n=2); patient refusal (n=2); and arthralgia, rash, and malaise (n=1 each). Hepatotoxicity generally was manifest as asymptomatic transaminase level elevation. Grade 3-4 hepatotoxicity was noted in four of 65 patients. Mean aspartase aminotransferase increased from 23 (baseline) to 67 U/L (during flutamide treatment) (P<.02); mean alanine aminotransferase level increased from 26 (baseline) to 94 U/L (during flutamide treatment) (P<.005). Flutamide toxicity was common. LFTs should be monitored during flutamide therapy. The role of flutamide in this treatment regimen may need to be reevaluated.