ObjectivesTo identify the asthma prevalence rate, the total healthcare and asthma-related treatment costs, and the medical and pharmacy costs associated with different asthma medication usage patterns in a managed-care organisation (MCO).Study design and participantsThe medical and pharmacy claims databases from a 400 000 member MCO were used. The medical claims database was searched from 1994 to 1996 for patients having at least one asthma medical claim in either the first or second diagnosis field of the medical claims, and the total healthcare and asthma-related costs were determined. A subpopulation with a more restrictive asthma definition was identified and their costs were also determined. In addition, the patterns of drug treatment were identified.Study perspectiveMCO perspective.ResultsThe mean total healthcare cost of caring for patients with asthma was significant and approximately twice the mean cost of all patients enrolled in the MCO. Using a broad definition of asthma, the mean (± standard deviation) annual total per patient healthcare cost was $US2511 ± 7314 and the annual asthma-related cost was $US679 ± 2247 (1996 values). Using a more restrictive definition of asthma, the mean annual total per patient healthcare cost was $US2653 ± 5268 and the asthma-related cost was $1026 ± 2447. There appeared to be a low overall use of asthma medications, especially anti-inflammatory formulations; <3% of patients with asthma were high users of anti-inflammatory inhalers.ConclusionsPatients with asthma are costly to managed-care organizations. Asthma-related costs constitute a minority (<30%) of the costs of caring for these patients, and under utilization of anti-inflammatory products by patients is widespread. Further research is needed to assess the cost impact of different asthma treatment patterns.