The recent introduction of selective alpha-adrenoceptor blockers adds a further therapeutic option for the treatment of benign prostatic hyperplasia (BPH). Tamsulosin, a selective alpha 1-blocker, has proved effective in relieving irritative and obstructive symptoms caused by BPH. To investigate whether the combination of tamsulosin with the anti-androgenic drug chlormadinone is of further therapeutic benefit, 80 patients randomly received tamsulosin 0.2 mg daily, chlormadinone 50 mg daily or a combination of tamsulosin 0.2 mg and chlormadinone 50 mg daily for 16 weeks. Greater improvement in subjective symptoms of BPH was obtained with either tamsulosin alone or in combination with chlormadinone than with chlormadinone alone. However, the greatest improvement in objective uroflowmetric data was obtained with chlormadinone in combination with tamsulosin. Thus, the combination of tamsulosin with chlormadinone appears to be more beneficial than either of these agents used as monotherapy. Further investigation is required to fully evaluate the therapeutic effects of this combination. After the trial period one-third of the chlormadinone and tamsulosin/chlormadinone-treated patients needed no further treatment due to the satisfactory relief of symptoms. At 12 months follow-up, however, one-fourth of the patients had undergone transurethral resection of the prostate (TUR-P) regardless of medication. This suggests a limitation of the medical treatment of BPH.