This study examines the patterns of 30-day hospital readmissions by race/ethnicity and multiple chronic conditions (MCC) burden among nonelderly adult patients. We used hospital discharge data of patients in the 18- to 64-year age group in 5 US states, California, Florida, Missouri, New York, and Tennessee, for 2009 from the Healthcare Cost and Utilization Project State Inpatient Database (HCUP-SID) of the Agency for Healthcare Research and Quality, linked to contextual and provider data from the Health Resources and Services Administration. A multilevel logistic regression model was used for data pooled over 5 states, adjusting for patient, hospital, and community characteristics. Controlling for other covariates, the study found that a higher MCC burden was associated with a higher all-cause 30-day readmission risk. We found considerable heterogeneity in levels of readmission risk among racial/ethnic subgroups stratified by chronic conditions. Among patients with a lowest MCC burden, African Americans had the highest risk of readmission, but with a higher MCC burden, the risk of readmission increased most for Hispanics.