Anaemia is frequent in breast cancer patients but often remains undiagnosed and untreated. To determine the incidence of anaemia a prospective survey of primary non-metastatic breast cancer patients who received at least four cycles of adjuvant, non-platinum multi-agent chemotherapy was conducted at 47 centres in Austria. Two hundred and forty seven patients were prospectively included between October 1999 and December 1999. Haemoglobin (Hb) levels were determined after surgery and prior to each cycle of chemotherapy. Treatment of anaemia (blood transfusion or epoetin alfa) during the observation period was at the physician's discretion. For the purpose of this study, patients were considered to be anaemic if their Hb was below 12 g/dl. At baseline (after surgery and before the first cycle of chemotherapy), 28.7% of all patients were anaemic. The only significant differentiating factor was the type of surgery. 37.9% of patients who underwent mastectomy were anaemic, whereas only 22.8% of patients who underwent breast conserving surgery were anaemic. Forty two percent of 176 patients with a Hb level of > or = 12 g/dl at baseline developed anaemia during adjuvant chemotherapy. The only factor that significantly influenced the development of anaemia during chemotherapy was the Hb level at baseline. The total incidence of anaemia in patients with primary breast cancer who underwent surgery followed by adjuvant multi-agent chemotherapy was 58.7%. Forty nine patients (20.2%), 48 patients (19.2%) and 48 patients (19.2%) showed a decrease in Hb levels by 1 g/dl, 1-2 g/dl and > 2 g/dl, respectively. Only 18.6% of the patients who were found to be anaemic received anaemia treatment. The two most important factors for developing anaemia are the kind of surgery and the Hb level prior to chemotherapy.