Temozolomide, an imidazotetrazine derivative, was given to 18 patients with low-grade non-Hodgkin's lymphoma (NHL) at a dose of 750 mg m-2 orally, divided over five consecutive days, escalated to 1000 mg m-2 over 5 days (i.e. 200 mg m-2 day-1) if no significant myelosuppression was noted at day 22 of the 28 day cycle. Fifty-six treatment cycles were given to 18 patients. The drug was well tolerated. Only one partial tumour response was documented. The patients were heavily pretreated but had chemoresponsive disease, as shown by a response rate of 69% among 13 patients who went on to receive alternative cytotoxic regimens. We conclude that temozolomide given in this schedule is inactive in previously treated low-grade NHL.