Seventy patients with clinical stage C carcinoma of the prostate were treated for 3 months with the gonadotropin-releasing hormone analog, goserelin acetate (Zoladex; Zeneca Pharmaceuticals, Macclesfield, UK) plus an antiandrogen (flutamide). Based on digital rectal examination (DRE), reductions of the size of the prostate and the tumor were noted in 91.4% of patients. Ultrasound demonstrated a decrease in prostatic volume between 0% and 62.5% (median 31%). Prostate-specific antigen (PSA) levels (Hybritech) decreased substantially (mean PSA of 31.3 ng/ml before, to a mean PSA of 1.4 ng/ml after hormonal treatment). A total of 64 patients subsequently underwent radical retropubic prostatectomy. Pathologically, only 9 patients (14.1%) had organ-confined disease (stage B), 34 (53.1%) had stage C tumors, and 21 (32.8%) had positive lymph nodes (stage D1). In 5 patients with nodal metastasis and 7 patients with seminal vesicle invasion, PSA levels after pretreatment were below 0.5 ng/ml. Maximal androgen blockade for a period of 3 months in clinical stage C prostate cancer induces a notable reduction in prostate size ("downsizing"). A "downstaging" effect, as suggested by DRE, ultrasound, and PSA, was not observed. Prospective studies with this treatment regimen should concentrate on a possible benefit concerning local and distant cancer control and survival.