The experience with single-agent gemcitabine in advanced or metastatic breast cancer is reviewed. In all studies, gemcitabine was administered as a 30 min intravenous infusion in cycles once a week for 3 weeks followed by 1 week of rest. In the first European study (gemcitabine 800 mg/m2/ week), of 40 evaluable patients, 14 were chemo-naive, 7 had received adjuvant chemotherapy, and 19 had received chemotherapy for metastatic disease. There were 3 complete responders and 7 partial responders (all independently validated by an external Oncology Review Board) for an overall response rate of 25.0% (95% Cl: 12.7%-41.2%). The median time to declaration of response was 1.9 months and the median duration of survival for all 40 efficacy-evaluable patients was 11.5 months. Haematological and non-haematological toxicities were particularly mild. WHO grade 3 and 4 toxicities included leukopenia (6.8% and 2.3% of patients), neutropenia (23.3% and 7.0%), AST (6.8% and 2.3%), ALT (18.2% and 0%, infection (0% and 2.3%), nausea and vomiting (25.0% and 2.3%), alopecia (2.3% and 0%). There was no grade 3 or 4 creatinine, proteinuria or haematuria. In the smaller US study (18 evaluable patients, all but one having received prior chemotherapy for stage IV disease) there were no responders. However, the mean dose delivered was very low (577 mg/m2/injection). In an ongoing European trial, with a starting dose of 1000 mg/m2, a number of partial responders have been seen in soft tissue, lung and liver. Gemcitabine's modest toxicity profile and single-agent activity make it an attractive candidate for trial in combination therapy in advanced breast cancer where treatment is currently given to palliate symptoms and improve quality of life