Protocols used to prepare patients with leukemia for bone marrow transplantation have the potential for cardiac toxicity due to high-dose cyclophosphamide and total-body irradiation. We have reported one regimen, combining cytarabine (5 mg/kg), cyclophosphamide (90 mg/kg), and total-body irradiation (900 cGy), which is relatively effective in the treatment of leukemia. To assess cardiac effects of this treatment regimen, we performed serial echocardiography and radionuclide ventriculography in 28 patients with leukemia (age range, 18-48 years; mean, 31; 21 males) undergoing allogeneic bone marrow transplantation. No significant change in left ventricular fractional minor axis shortening or increase in left ventricular diastolic dimension was seen with weekly echocardiography. At an average of 77 days (range, 28-358) after transplant, repeat radionuclide ventriculography in 17 patients revealed no significant change in resting left ventricular ejection fraction compared to that on admission to the hospital (58% +/- 6.8% vs 56% +/- 8.0% SD; P = not significant). In seven of these 17 patients (41%), resting ejection fraction fell between baseline and discharge (from mean of 60% to 50%). Resting ejection fraction in four of these patients (23% of the entire group) fell into the abnormal range (from mean of 56% to 44%; lowest, 41%). Ten patients also had exercise radionuclide ventriculography and all had normal responses (greater than 5% increase with exercise) pre- and post-transplant. We conclude that this effective bone marrow transplantation regimen has little apparent short-term cardiac toxicity in the majority of patients; since a few patients do exhibit a deterioration in left ventricular function, continued cardiac surveillance is probably indicated in posttransplant patients.