We report on the incidence of emergency department (ED) asthma presentations and admissions to the Lincoln Hospital, located in the South Bronx of New York City, during the 1999 eradication program of the mosquito vector for West Nile virus. Spraying of Malathion and Resmethrin occurred in the hospital's geographic area over 4 days in September 1999. During that time, 1318 pediatric and adult patients were seen in the ED for asthma-related symptoms. Of these, 222 (16.8%) were hospitalized. Emergency department visits, during days when spraying occurred, were compared with visits during days when no spraying occurred. Comparisons were made with previous years as a reference point. Findings showed that the spraying of insecticides did not increase the rate or severity of asthma presentations as measured by the Lincoln Hospital's ED asthma census or hospital admissions for asthma.