Background: Late-onset noninfectious pulmonary complications (LONIPCs) after allogeneic hematopoietic cell transplantation (HCT) contribute to posttransplant mortality, morbidity, and decreased quality of life. The effect of newer HCT approaches including reduced intensity and umbilical cord on the incidence and outcome of LONIPC has not been studied. We hereby present a study evaluating the incidence, risk factors, and outcomes of LONIPC in a recent cohort of allogeneic HCT recipients. METHODS.: We reviewed the incidence and outcomes of LONIPCs in 451 consecutive adult patients who received allogeneic HCT between 2002 and 2007 and survived for 80 days or more after transplant. Results: Seventy-four patients developed LONIPCs at a median of 177 days (range, 81-1017 days) after HCT. The 1-year cumulative incidence of LONIPCs was 13% (95% confidence interval, 10%-16%). Of the 451 patients, LONIPCs occurred in 21% receiving myeloablative vs. 12% with nonmyeloablative conditioning. Myeloablative conditioning and chronic graft-versus-host disease were associated with significantly higher risks of LONIPC, but age, graft type, and acute graft-versus-host disease were not identified as risk factors. LONIPCs manifest as diffuse alveolar hemorrhage (DAH, n=28), idiopathic pneumonia syndrome (IPS, n=19), bronchiolitis obliterans (n=22), and other uncommon syndromes (n=5). One-year survival was 77% for patients with bronchiolitis obliterans, 37% for patients with IPS, and 36% for patients with DAH. Three-year survival was significantly worse for recipients with LONIPCs compared with those without LONIPCs (34% vs. 57%, P<0.01). Conclusion: LONIPCs in allogeneic HCT recipients include a heterogeneous group of diseases with varying clinical courses and prognosis. LONIPCs, particularly IPS or DAH, are associated with high mortality after HCT.