Indices of air pollution, meteorological conditions and airborne allergens were correlated with emergency room census and hospitalizations for asthma at the Childrens Hospital of Los Angeles (CHLA) during a six-month period encompassing high and low periods of air pollution. In addition, patients in residence at the Sunair Home for Asthmatic Children (SHAC) were studied during a 10-day peak air pollution period. Increases in asthma emergency room visits and hospitalizations correlated significantly with increases in nitric oxide, coefficient of haze, hydrocarbons, Santa Ana wind conditions and total airborne allergen counts. Significant correlations were also found with decreases in ambient levels of O3, SO2, temperature and relative humidity. Among SHAC patients morning peak flow levels were significantly lower during the 10-day peak pollution period than during two control periods of low pollution. However, neither differences in clinical symptoms experienced by these patients nor their need for additional medication were observed.