Objective: This study was conducted to test the effectiveness of a theory-based interactive voice response (IVR) intervention to improve adherence to controller medications among adults with asthma.Methods: Fifty participants aged 18 to 65 years who had a physician diagnosis of asthma and a prescription for a daily inhaled corticosteroid, attended a baseline visit and a final visit 10 weeks later. Participants randomized to the intervention group received 2 automated IVR telephone calls separated by one month, with one additional call if they reported recent symptoms of poorly controlled disease or failure to fill a prescription. Calls were completed in less than 5 minutes and included content designed to inquire about asthma symptoms, deliver core educational messages, encourage refilling of inhaled corticosteroid prescriptions, and increase communication with providers. Adherence was tracked during 10 weeks, with objective measures that included either electronic monitors or calculation of canister weight. Participants completed the Asthma Quality of Life Questionnaire, the Asthma Control Test, and the Beliefs in Medications Questionnaire (BMQ) during both visits.Results: Adherence was 32% higher among patients in the IVR group than those in the control group (P ؍ . Patients often do not adhere to treatments for chronic health conditions, with the consequence that many conditions are poorly controlled. In the treatment of asthma, fewer than half of prescribed daily controller medication is typically taken by patients.1,2 In a report about refill patterns among 5500 patients with asthma, only 43% filled their inhaled corticosteroid more than once during 12 months. 3 In another study, each 25% decrease in refilled medication was accompanied by a doubling of the hospitalization rate. 2 Adherence rates among children are similarly poor 4,5 and remain so even in the face of recent exacerbation. 6 Considerable attention has been directed at changing health behavior and increasing adherence to treatments for chronic health conditions. The World Health Organization in 2003 published a call for action to improve treatment adherence across diseases, continents, and cultures, 7 and the This article was externally peer reviewed.