We used a clinical score, the pulmonary index (PI), in the emergency room assessment of children with acute asthma. The PI was derived from respiratory rate, wheezing, inspiratory-expiratory ratio, and use of accessory muscles. Patients were treated with a beta-adrenergic drug and were assessed before and at 15-minute intervals after treatment using clinical examination, PI, and spirometry. The PI before treatment correlated significantly with the mean percent of forced expiratory volume in the first second to forced vital capacity ratio. The PI 30 minutes after treatment correlated significantly with all tests of pulmonary function performed. The PI is a simple score that is easily derived from clinical observation.