Although childhood hospitalizations for asthma are common, there are few detailed temporal and demographic descriptions of these hospitalizations. To relate temporal patterns of asthma hospitalization in young children to admission age, sex, comorbid infection, and race. Retrospective analysis of 151,391 New York State hospitalizations with a principal diagnosis of asthma between January 1, 1990, and December 31, 2004, in children younger than 5 years. Admission patterns across time were related to admission age, sex, race, and comorbid diagnoses of common infections. Although the overall hospitalization rate decreased, it was still 63.8 per 10,000 in 2004. Higher hospitalization rates were consistently observed in children younger than 3 years, African Americans, and boys. Fall increases and summer declines in overall monthly hospitalization rates and monthly median ages exemplified the seasonality observed in the study population. However, admissions with concomitant common infections peaked in the winter, not fall months. Sex did not affect the observed seasonality. Compared with white patients, African Americans not only manifested more than 3-fold higher hospitalization rates but also more repeated hospitalizations. The concurrent cyclical increases in median age and monthly admissions suggest that seasonal factors affecting older children may relate to fall increases in asthma admissions. These fall peaks are not accounted for by recognizable concomitant common respiratory tract infections. Understanding the basis for these seasonal variations may lead to prevention strategies that could decrease asthma admissions. Asthma hospitalizations in young children continued to be highly prevalent in New York State, especially in African American patients.