Diaziquone (AZQ), a synthetic quinone with demonstrated activity against acute nonlymphocytic leukemia (ANLL), primary CNS tumors, and non-Hodgkin's lymphoma (NHL), is virtually devoid of nonhematopoietic toxicity at conventional doses. As a prelude to its inclusion into bone marrow transplant (BMT) preparative regimens, a phase I study of high-dose AZQ with autologous BMT (ABMT) was performed. Patients with refractory solid tumors and lymphomas were treated with a single 24-hour infusion of AZQ at 50 to 355 mg/m2 in dose escalations of 20%. Fifty-six patients received 69 courses. Those receiving greater than 60 mg/m2 had nadir granulocyte and platelet counts less than 500/microL and 20,000/microL, respectively. Nausea, vomiting, stomatitis, and diarrhea were mild, transient, and not dose-related. Transient minimal elevations of liver function tests were seen in five patients and were also not dose-related. The maximally tolerated dose (MTD) of high-dose AZQ was found to be 245 mg/m2, with nephrotoxicity being dose-limiting. Significant azotemia was seen in four of 12 patients treated at 295 and 355 mg/m2, including fatal anuric renal failure in three of these patients. Reversible proteinuria also occurred in 24 of 26 courses above 150 mg/m2, including nephrotic range proteinuria in eight courses, all at doses of 205 to 355 mg/m2. The proteinuria was also associated with multiple proximal tubular defects including generalized aminoaciduria and proximal renal tubular acidosis. There were six early deaths including two of early renal failure (295 and 355 mg/m2), two of sepsis (205 and 245 mg/m2), one of a pulmonary embolus (85 mg/m2), and one of progressive disease (60 mg/m2). Of 50 patients who were assessable for response, there were seven responses including two of 10 with primary CNS tumors, one of 12 with malignant melanoma, one of five with non-small-cell lung carcinoma, two of two with breast carcinoma, and one of one with ovarian carcinoma. Because of its activity in ANLL and NHL and its unique toxicity spectrum, high-dose AZQ may improve the efficacy of current BMT preparative regimens without significantly increasing their nonhematopoietic toxicity.