Interferons alpha and beta have been reported to cause tumor regression in a small proportion of patients with recurrent glioma. Eflornithine, an irreversible inhibitor of ornithine decarboxylase, reduces cellular polyamine levels and has also been reported to cause tumor regression in patients with recurrent anaplastic astrocytoma and glioblastoma multiforme. In vitro evidence suggests that interferon and eflornithine are synergistic. In this phase II trial, we investigated the combination of recombinant alpha interferon (36 x 10(6) units/m2 subcutaneously days 3 to 7) and eflornithine (2.25 g/m2 QID PO days 1 to 7) repeated every 28 days. All 29 patients entered in the study were evaluable for toxicity and efficacy. Toxicity consisted primarily of fever, chills, myalgia, weakness and fatigue as well as cortical dysfunction including somnolence, confusion, and exacerbation of underlying neurologic deficits. One patient died from cerebral herniation attributable to interferon. None of the patients experienced objective tumor regression. Seven patients (24%) were stable for more than six months, but the disease stability could also be explained by indolent underlying disease or inability to distinguish recurrent tumor from delayed radiation effects. Intermittent high-dose recombinant interferon alpha plus eflornithine demonstrated no definite antitumor effects in this trial.