Eighty-eight patients with advanced breast cancer were retrospectively reviewed to compare estrogen receptor (ER) data with response to cytotoxic chemotherapy. All assays were done in a single laboratory. All patients were cared for at a single institution. Thirty-four patients were treated with chemotherapy, 30 of whom were evaluable for response by criteria of the Eastern Cooperative Oncology Group (ECOG). Of 16 ER-positive patients, 12 (75%) responded; of 14 ER-negative patients, six (43%) responded (P < 0.05). The two groups did not differ significantly in chemotherapy received, menopausal status, site of predominant disease, stage at diagnosis, or disease-free interval. Response to cytotoxic chemotherapy does not appear to correlate with ER status.