PURPOSE: Acute chest syndrome (ACS) is a common complication among pediatric inpatients with sickle cell disease and vaso-occlusive crisis (VOC). However, little is known about the factors associated with ACS complication. The present study assessed the epidemiological features of children hospitalized with VOC and ascertained factors associated with ACS complication. METHODS: Hospital discharge records of patients with VOC aged <20 years were obtained for the years 2003, 2006, 2009, and 2012 from the Kids' Inpatient Database. Data were weighted to estimate the annual hospitalization rates with respect to gender and race/ethnicity in the United States. Multivariable logistic regression was conducted to ascertain factors associated with ACS complication after adjusting for patient and hospital characteristics. RESULTS: The total annual hospitalizations for VOC increased from 22,511 in 2003 to 24,292 in 2012. Multivariable logistic regression analysis showed that children aged 5-9 years had 2.59 times higher odds of ACS than children aged 15-19 years (95% confidence interval [CI], 2.32-2.88). Comorbidity of asthma (odds ratio [OR], 1.42; 95% CI, 1.31-1.54) and obstructive sleep apnea (OR, 1.70; 95% CI, 1.31-2.20) were associated with ACS development. ACS was also associated with male gender and the summer and fall seasons. CONCLUSION: We reported nationwide estimates of the annual hospitalization rate for childhood VOC in the United States and demonstrated the major risk factors associated with ACS complication. Vigilance is needed for ACS complications in high-risk VOC admissions.