A phase II trial was instigated to investigate the antitumour activity, the safety and the pharmacokinetic parameters of RFS2000, a recently identified oral topoisomerase I inhibitor, given once daily (1.5 mg/m(2)/day) as first-line chemotherapy treatment for patients with advanced glioblastoma multiforme (GBM). Between 9 March and 15 September 2000, 17 patients were entered onto the trial. 15 patients were considered eligible. A total of 49 cycles (range 1-8) were administered. Grade 3-4 toxicity was observed in 5 patients. Neutropenia and thrombocytopenia were common toxicities. Pharmacokinetic analysis showed that 9-nitro camptothecin (9-NC) could be detected in the plasma and is progressively converted into 9-amino-camptothecin (9-AC). The response rate was poor, with 5 patients experiencing tumour stabilisation and 10 progressing. Thus, the results do not support the further evaluation of RFS2000 as a single agent in patients with recurrent GBM.