Allogeneic hematopoietic cell transplantation (HCT) using reduced-intensity conditioning (RIC) has lower morbidity and mortality compared to transplantation using myeloablative conditioning (MAC). The syndrome of alveolar hemorrhage, a life-threatening pulmonary complication of HCT, has not been well described after RIC HCT. We reviewed prospectively collected data on 206 RIC and 1112 MAC HCT performed between 1995 and 2004 to study the impact of conditioning regimen on the clinical features and outcome of alveolar hemorrhage. Alveolar hemorrhage occurred in 18 RIC HCT recipients (cumulative incidence 8% (95% confidence intervals (CI), 5-11%)) and 85 MAC HCT recipients (cumulative incidence 7% (95% CI, 6-8%), P=0.56). The clinical presentation of hemorrhage in both cohorts was similar. Survival at 60 days from the onset of hemorrhage was 28% (95% CI, 7-49%) for RIC group compared to 26% (95% CI, 17-35%) after MAC HCT (P=0.56). Reducing the intensity of preparative regimen does not protect against post transplant alveolar hemorrhage. Alveolar hemorrhage occurring after RIC or MAC HCT has similar incidence, clinical presentation, and associated high mortality.