We carried out a double blind multicentre clinical trial in which 171 patients with advanced breast cancer were randomized to receive tamoxifen (30 mg/day) + bromocriptine (5 mg/day) or tamoxifen + placebo. No difference was found in the overall response rates in the two groups (37.5% for placebo; 38% for bromocriptine) or in subgroups (breast tumours, lymph nodes, lung, bone, skin metastases). Tolerability was good in both groups. Within the limits of the statistical power of the test (80%), our results do not show any benefit when bromocriptine was added to tamoxifen.