OBJECTIVES: Asthma patients' lack of adherence to inhaled corticosteroids (IC) contributes to treatment failure and over $6.2 billion in associated costs. In disease states such as hypertension, adherence rates =80% are related to clinical success. Similar adherence rates for IC in asthma patients have not yet been determined. This study was designed to assess the relationship between IC adherence rate and Total Medical and Drug Costs (TMDC). METHODS: Data were from a commercial, integrated pharmacy/medical claims database. Patients ranging from 4 to 55 years with at least 2 claims for an IC, a 120-day benefit history, and a 360-day continuous enrollment were included. Patients were excluded if they were also coded for non-asthma-related pulmonary diseases. Age, gender, and concomitant drug/disease information were collected. The adherence rate was defined as [Total days supply of IC/(last RX date less first RX date + last days supply)]. TMDC included drug, hospital, physician visit and lab costs. The number of Disease Related Events (DRE) was also determined. ANOVA or equivalent tests, along with multiple regression techniques were used to test hypotheses. RESULTS: Six hundred forty-three patients were identified. The mean age was 30.5 ±15.8, with 43.5% males. We classified 8.5% of patients as 80-99% adherent, 8.2% between 60-79% adherent, 14.9% between 40-59% adherent, and 70.6% of patients were 39% adherent. There was no significant difference in the TMDC among adherence quintiles. The regression demonstrated a statistically significant correlation (r=0.76) between age (p<0.0001), number of medications (p<0.0001), co-morbidities (p<0.0001), use of budesonide inhaler (p=0.0081) or long-acting beta agonists (p=0.0017) against the log of TMDC. There were no items inversely correlated to TMDC. There was no difference in DRE between patients <80% or = 80% adherent. (c2=0.3511, 1 d.f., p=0.5535). CONCLUSION: Based on this study, there was not significant linear correlation between adherence to IC and TMDC.