OBJECTIVES: The aims of this study were to estimate what portion of asthma patients are using quick-acting asthma medications inappropriately and to examine how the inappropriate use varies with age and sex. METHODS: Prescribed medicine data of 1996-2000 from the Medical Expenditure Panel Survey (MEPS) are retrospectively analyzed. The survey is on-going project, sponsored by the Agency for Health care Research and Quality. Non-institutionalized U.S. citizens of 5 or older who had used quick-acting asthma relievers in a given year were identified and further classified as 'inappropriate users' if high doses of short-acting beta-agonists were taken in conjunction with low doses of inhaled corticosteroids. RESULTS: During the period of 1996-2000, a total of 2,390 subjects reported that they had used quick-acting asthma relievers per year. Of those, 284 (11.88%) were 65 years of age or older and 862 (36.07%) were five through 17 years of age. The remaining 1244 (52.45%) were 18 through 64 years of age. More than half of the subjects were females (59.21%). About six percent (95%CI: 5.07-6.87%) of the users of quick-acting asthma relievers were using the medication inappropriately. Asthma patients with 65 years of age or older were subject to a higher risk of medication misuse (9.09 ± 2.32%). Young children with ages of 5 through 17 years were subject to a lower risk (4.16 ± 0.93%). Although males were subject to a slightly lower risk than females (95%CI: 4.10-7.87% vs. 5.19-8.80%), the difference was not statistically significant. CONCLUSIONS: Despite the existence of national guidelines on the proper use of shorting-acting asthma inhalers, asthma patients who use short-acting asthma inhalers are at a substantial risk of inappropriate use. Future national policies should address ways of improving patient compliance in the use of shorting acting asthma inhalers.