Twenty-five patients with malignancies resistant to conventional chemoradiation therapy or for which no effective therapy is known were treated with escalating doses of thiotepa (135-1215 mg/m2 iv over 3 days) followed by reinfusion of previously cryopreserved autologous bone marrow. The hematological and nonhematological toxic effects, therapeutic effects, and pharmacokinetics of this regimen were evaluated. Granulocyte (greater than 500/microliter) and platelet (greater than 20,000/microliter) count recovery occurred at a median of 16 (range, 11-38) and 18.5 (range, 11-40) days after marrow reinfusion, respectively. Six patients experienced severe infection, four of which were fatal. One patient died due to intracranial hemorrhage. Toxicity to the gastrointestinal and central nervous systems was dose-limiting, and the maximum tolerated dose of thiotepa was 1005 mg/m2. Objective tumor regression occurred in six of the patients. Serum thiotepa concentration peaked immediately after infusion and declined rapidly in a biphasic manner. No relationship between thiotepa serum concentration or pharmacokinetic parameter estimates was observed for tumor response or toxicity. High-dose thiotepa and autologous bone marrow transplantation may represent an alternative therapeutic modality for patients with advanced cancer.