OBJECTIVE Although docetaxel (DOC) plus prednisone is currently the treatment of choice for hormone-refractory prostate cancer (HRPC), no standard therapy is available for those patients who progress during DOC treatment. The aim of this study was to evaluate whether the addition of estramustine (E) can overcome DOC resistance. METHODS Patients who had not responded to DOC in a previous randomised phase II trial received a one-hour intravenous infusion of DOC 70 mg/m(2) on day 2 in combination with oral E 840 mg/day divided into three daily administrations on days 1-5. The primary endpoint was a >50% decrease in PSA; the secondary endpoints were biochemical progression-free survival, overall survival, the objective response rate, and toxicity. RESULTS A biochemical response was observed in 52% of the 25 patients evaluable for response. The only grade 4 event was a cerebral stroke that occurred a few days after the administration of the first treatment course. Treatment discontinuation due to worsened compliance was observed in the patients who received a higher cumulative number of courses. CONCLUSIONS Our findings suggest that the addition of E may be useful in selected HRPC patients resistant to DOC alone.