Study of intra-arterial BCNU in 12 patients with recurrent glioblastoma multiforme and 5 patients with recurrent anaplastic astrocytoma already treated by surgery and radiotherapy indicates that the risk of BCNU toxicity can be reduced by the use of relatively low doses (160-180 mg/m2) of BCNU, the use of dextrose as solvent, selective injections of BCNU, and fast "bolus" injections of drug. No certain toxic effects of BCNU were observed in the 17 patients treated this way. Anaplastic astrocytomas, particularly in young patients, seem to respond relatively well to this treatment.