Objectives: To determine if there are racial/ethnic differences in the rates of appendiceal rupture among the children of two large states. Because rupture is primarily due to delayed diagnosis, differences would suggest disparities in timely access to quality emergency care. Methods: This was an observational, cross-sectional analysis of full-year samples of acute appendicitis cases from California and New York children 4 to 18 years old. Racial/ethnic groups were compared for risk of appendiceal rupture adjusted for biological factors both before and after adjustment for the following socioeconomic, hospital, and admission characteristics: income, insurance, hospital type, and admission source. Results were interpreted in light of census data on the proportion of immigrants in each racial/ethnic group. Results: Compared with white children with acute appendicitis, Hispanic and Asian children have higher odds of rupture in California, whereas Asian and black/African American children have higher odds in New York. These differences roughly parallel the within-state proportion of immigrant children in these groups. Adjustments for family, socioeconomic, and hospital characteristics attenuate but do not eliminate disparities. Conclusions: The authors found evidence of significant racial/ethnic disparities in rate of appendiceal rupture, an important and preventable outcome, in two large but dissimilar states. Immigrant groups may be most at risk for delayed emergency care. Future research should focus on immigration and acculturation as risk factors for appendicitis rupture in children.