We investigated a cluster of five deaths of adolescents from asthma in St. Louis during a 3-month period in 1987. Although the cluster represented a statistically significant increase in the number of asthma deaths in this age group over that observed in previous years, no common exposure to environmental, infectious, or therapeutic agents could be identified. The patterns of hospital admissions for asthma and emergency room visits at the two pediatric hospitals in the community did not suggest an increase in the frequency or severity of asthma during this time. Despite the lack of evidence for common exposure, the decedents shared many personal and medical characteristics. All decedents were black patients and were of lower socioeconomic status. All were adolescents and were responsible for regulating their own medication schedules. Lack of appreciation of the severity of their asthma by medical personnel and the patients' families was evident. For example, two patients with severe asthma had not been prescribed inhaled corticosteroids. In addition, the four decedents tested had markedly subtherapeutic or zero serum theophylline levels measured at the time of the fatal episode, even though appropriate amounts of theophylline had been prescribed. Their theophylline levels were substantially lower than levels in patients of the same age observed at the emergency room or hospitalized for asthma during the same time period. Continued efforts to educate adolescent patients, their families, and medical care providers about the treatment of asthma are warranted.