The objectives of this cross-sectional study were to measure health literacy and its associations with asthma patients' assessments of care and their desire to participate in making decisions about their treatment. A total of 175 patients completed the Test of Functional Health Literacy in Adults and questions about satisfaction with asthma status, access to care, quality of care, and the desire to participate in treatment decisions. Patients' mean age was 42 years and 83% were women. Lower literacy was associated with less satisfaction with asthma status and worse assessment of quality of care received for asthma and other medical conditions (p < or = .005). Patients with lower literacy also were more likely not to want to participate in decisions about their care (OR .29, 95% CI .13, .65). These relationships persisted after controlling for demographic and asthma characteristics. These results provide additional incentives for physicians to find better ways to explain asthma treatments to low literacy patients.