Cromolyn sodium was administered by inhalation 4 times a day to 53 severely asthmatic children for periods ranging from 10-43 mo. The patients were seen at follow-up visits at least once a month through the entire study period. At the end of the study, cromolyn sodium was effective in controlling asthma by reducing the level of asthma symptoms, such as coughing, wheezing, sleep disturbance and sputum output. There was a reduction in the patients'' requirements for concomitant anti-asthma medications (including corticosteroids) and the number of hospitalizations and school absences.