A randomized trial was performed to determine if therapy with tamoxifen (TAM) plus fluoxymesterone (FLU) was more efficacious than TAM alone for postmenopausal women with metastatic breast cancer. Patients failing TAM could subsequently receive FLU. The dose of both drugs was 10 mg orally twice daily. Objective responses were seen in 50 of 119 (42%) TAM patients and 64 of 119 (54%) TAM plus FLU patients (two-sided P = 0.07). Time to disease progression was better for TAM plus FLU (medians: 11.6 versus 6.5 months; Cox model, P = 0.03). Duration of response and survival were similar in the two treatment arms. Among 97 patients with estrogen receptor (ER) of 10 or greater and 65 years of age or older, there were highly significant advantages for treatment with TAM plus FLU in both response rate and time to progression. Of particular note is that in this patient group TAM plus FLU showed a survival advantage (Cox model, P = 0.05). Although these data require confirmation in a prospective randomized trial, they suggest that there is a substantive therapeutic advantage for TAM plus FLU over TAM alone in elderly women with ER of 10 fmol or greater.