The results of nine phase II trials of docetaxel in the first- and second-line treatment of patients with advanced breast cancer are summarized. All 316 patients included in this report received docetaxel at a dose of 100 mg/m2 administered over 1 h every 3 weeks on an outpatient basis. One hundred and fifty-four patients received docetaxel as first-line therapy for advanced disease, half of whom had received prior adjuvant chemotherapy (finished at least 1 year previously). An overall response rate of 59% (95% CI: 51-67) was achieved in these patients, with a median duration of response of 8.3 months and a median time to progression of 4.9 months. Similar results were seen in a subgroup of 68 patients with liver metastases. Among the 162 patients given docetaxel as second-line therapy, 134 had strictly defined anthracycline-resistant disease; 73 had liver metastases. The combined overall response rate for anthracycline-resistant patients in two US studies was 48% (95% CI: 37-59) while that in a multicenter French study was 29% (95% CI: 18-44). The median duration of response in each case was 6.3 and 5.5 months, respectively, with an overall median survival duration of 11 and 10 months, respectively. Among patients with liver metastases, second-line treatment with docetaxel achieved an overall response rate of 32%, a median duration of response of 7.8 months and a median survival duration of 9 months. These results for docetaxel as both first- and second-line therapy are comparable with those achieved with doxorubicin and are particularly promising in patients with liver metastases and anthracycline-resistant disease.