Despite generally high cure rates in patients with metastatic germ cell cancer, patients with progressive disease on first-line cisplatin-based chemotherapy or with relapsed disease following high-dose salvage therapy exhibit a very poor prognosis. Irinotecan has shown antitumour activity in human testicular tumour xenografts in nude mice. We have performed a phase II study examining the single agent activity of irinotecan in patients with metastatic relapsed or cisplatin-refractory germ cell cancer. Refractory disease was defined as progression or relapse within 4 weeks after cisplatin-based chemotherapy or relapse after salvage high-dose chemotherapy with autologous stem cell support. Irinotecan was administered at a dose of 300 (-350) mg m(-2) every 3 weeks. Response was evaluated every 4 weeks. Fifteen patients have been enrolled. Median age was 35 (19-53) years. Primary tumour localisation was gonadal/mediastinal in 12/3 patients. Patients had been pretreated with a median of six (4-12) cisplatin-containing cycles and 13 out of 15 patients had previously failed high-dose chemotherapy with blood stem cell support. Median number of irinotecan applications was two (1-3). Fourteen patients are assessable for response and all for toxicity. In one patient, no adequate response evaluation was performed. Toxicity was generally acceptable and consisted mainly of haematological side effects with common toxicity criteria 3 degrees anaemia (two patients), common toxicity criteria 3 degrees leukocytopenia (one patient) and common toxicity criteria 3 degrees thrombocytopenia (three patients). Common toxicity criteria 3/4 degrees non-haematological toxicity occurred in five patients (33%): 1 x diarrhoea, 2 x alopecia, 1 x fever and in one patient worsening of pre-existing peripheral polyneuropathy from 1 degrees to 4 degrees. No response was observed to irinotecan therapy. Currently, 13 patients have died of the disease and two patients are alive with the disease. The patients included in our study exhibit similar prognostic characteristics as patients treated in previous trials evaluating new drugs in this setting. Irinotecan at a dose of 300-350 mg m(-2) every 3 weeks appears to have no antitumour activity in patients with cisplatin-refractory germ cell cancer and, thus, further investigation in this disease is not justified.