The objectives of this study were to determine the rate and risk factors for hospital readmission after inpatient treatment for bronchiolitis. We conducted a retrospective cohort study from 2000 to 2002. The readmission rate within 30 days was 3.7% (95% Confidence Interval: 2.1%-6.0%). Readmission was not associated with age, prematurity, respiratory syncytial virus status, receipt of intensive care, or the observation period off supplemental oxygen. Those who required supplemental oxygen had a lower risk of readmission. Identifying children at risk for readmission is challenging. Children who did not require supplemental oxygen may be at greater risk because they are progressing in their illness.