The purpose of this study was to improve asthma care and outcome in an inner-city emergency department. Consecutive adult patients (19,802) presenting with the diagnosis of acute asthma exacerbation to an inner-city municipal hospital emergency department, between July 1991 and December 1993, were prospectively evaluated. These patients were compared to a historical control group of 7923 consecutive asthma emergency department patients presenting in the year prior to our intervention. An asthma treatment guideline was implemented through a continuous quality improvement process. Asthma relapse rate and admission rate were obtained before and after the guidelines were instituted. Data after interventions were also prospectively compared to asthma outcomes at all other New York City municipal hospital emergency departments. After intervention, mean monthly asthma relapse rates showed a significant reduction from 12.18% to 7.83% (p < 0.001). A similar decrease was also noted in the monthly asthma admission rate, from 4.85 to 3.90 per 100 emergency department visits (p < 0.05). Asthma treatment guidelines along with continuous quality improvement techniques can significantly improve the outcome of inner-city emergency department asthma patients.