The authors report that 4 out of a series of 56 patients (7.1%) treated with gemcitabine developed an unexplained non-cardiogenic pulmonary distress syndrome most likely related to gemcitabine. One further patient developed ventricular arrhythmia immediately after gemcitabine exposure, leading to cardiac arrest. Between 1995 and 1998 56 patients with locally advanced or metastatic carcinoma were treated with gemcitabine. The patients suffered from breast cancer (n = 17), pancreatic cancer (n = 17), lung cancer (n = 12), cancer of unknown primary (n = 5), ovarian cancer (n = 2), oral cavity cancer (n = 2) and cancer of the bladder (n = 1). Their median age was 55 years, and there were 33 female and 23 male patients. Fifteen patients had been pretreated with radiation therapy: 2 had received radiation therapy involving the mediastinum as treatment for non-small-cell lung cancer and cancer of unknown origin respectively, 11 patients had had prior neoadjuvant or adjuvant radiation therapy of the chest wall for breast cancer and 2 patients had received radiation therapy for head/neck cancer. All patients received gemcitabine on days 1, 8 and 15 and this was repeated on day 29 at a dose of 1000 mg/m(2) as a 30-min infusion in 250 ml isotonic NaCl. In 4 patients gemcitabine treatment was combined with cisplatinum, in 7 patients with a somatostatin analogue and in 1 patient with epirubicin. All other patients received gemcitabine as a single agent. We assume that the pulmonary or cardiac toxicity of 5 patients was related to gemcitabine. In 3 patients re-exposure resulted in repeated toxicity. One patient did not receive gemcitabine again because of the life-threatening nature of the primary response. Two patients had received prior radiation to the mediastinum with 62 Gy and 50 Gy respectively, 3 years and 1 year before gemcitabine application. In our experience pulmonary toxicity after gemcitabine treatment is more common than initially anticipated. Gemcitabine should be used with caution in patients who have received prior radiation to the mediastinum.