This trial was conducted to determine if the reported superiority of tamoxifen (TAM) plus prednisolone (PRDLN) over TAM alone in postmenopausal women with metastatic breast cancer could be corroborated. A total of 326 patients were randomized on a double-blind trial to TAM (10 mg twice daily) plus placebo or TAM plus PRDLN (5 mg twice daily). Six patients (2%) were disqualified. Considering 256 patients with measurable or evaluable disease, objective responses were seen in 48 (38%) of 126 TAM patients and 61 (47%) of 130 TAM plus PRDLN patients (chi-square, P = 0.15). Considering all 320 evaluated patients, median time to disease progression was 11 months for TAM and 10 months for TAM plus PRDLN (log rank, P = 0.81), and median survival time was 35 and 32 months, respectively (P = 0.40). Covariate analyses showed no significant association between treatment and outcome. Weight gain and edema were significantly greater with TAM plus PRDLN. The addition of PRDLN to TAM is not advocated for the management of postmenopausal women with metastatic breast cancer.