Pulmonary disease is a significant morbidity among childhood cancer survivors. The aim of this study was to characterize the pulmonary dysfunction experienced by childhood cancer survivors treated with bleomycin. A cross-sectional analysis of pulmonary function testing (PFT) in survivors treated with bleomycin was preformed. The most recent posttherapy PFT was assessed. Spirometry and lung volumes were categorized as normal, restrictive, obstructive, or mixed. Diffusing capacity of carbon monoxide (DLCO) was categorized as normal or abnormal. PFT data of 143 survivors was analyzed. PFTs were performed a median of 2.3 years (interquartile range, 1.4 to 4.9) from completion of therapy. Spirometry was abnormal in 58 (41%), only 5 (9%) had respiratory symptoms. Forty-two (70%) had obstructive, 11 (18%) restrictive, and 5 (9%) mixed ventilatory defects. The majority of abnormalities were mild (91%). DLCO was abnormal in 27. Reductions were mild in 96%. Patients with a history of relapse were more likely to develop abnormalities in spirometry and/or DLCO (odds ratio=5.02, 95% confidence interval: 1.3-19.4, P=0.01; odds ratio=3.47, 95% confidence interval: 1.01-11.9, P=0.03). Asymptomatic abnormalities of PFT are common among childhood cancer survivors treated with bleomycin and associated with a history of relapse. Research studying the risk for clinical progression of this dysfunction is warranted.