Malignant infantile osteopetrosis (MIOP) is a rare disorder caused by dysfunctional osteoclasts. The classic MIOP features, such as frontal bossing, micrognathia, and small thorax, may place these children at risk for developing obstructive sleep apnea (OSA) and chronic hypoxemia. To objectively document OSA, airway evaluations were performed; results impacted management. We reviewed the records of 7 MIOP patients treated at St Jude. Six underwent polysomnograms during prehematopoietic stem cell transplantation (HSCT) evaluation. To determine the existence of a relationship between OSA and radiologic imaging, initial chest radiographs and bone mineral density studies were reviewed. Pre-HSCT patients had a median apnea-hypopnea index of 17.51 (normal, 0 to 2), with <25% being central events, thus indicating OSA. The median minimal oxygen saturation was 79%, indicating intermittent hypoxemia. Neither chest radiographs nor bone mineral density correlated with severity of OSA. Four patients received tracheostomies before or during HSCT. Three surviving children underwent polysomnograms 1 year after HSCT, and median apnea-hypopnea index was 1.3, indicating near to complete resolution of OSA. Resolution of OSA may have been multifactorial. Using a quantitative approach, we demonstrate that MIOP children have OSA and hypoxemia; thus, these children should have airway evaluations and treatments to potentially reduce the risk of life-threatening pulmonary complications.