We report on 2 patients in whom intractable hematuria was caused by carcinoma of the prostate. Since the hematuria failed to respond to conservative measures, intravesical 1 per cent alum irrigation was used. Hematuria resolved in both patients and no toxicity was observed. Intravesical alum irrigation should be considered in any patient with significant hematuria secondary to carcinoma of the prostate in whom conservative therapy has failed.