Our goal was to understand which features of asthma controller medications are important to patients. We used a cross-sectional survey of primary care patients (N = 394) with the diagnosis of asthma. Using conjoint or "trade-off analysis," we measured patient preferences for hypothetical asthma controller medications based upon their route and frequency of administration, and need for blood test monitoring. Patients were not willing to use medications that required blood test monitoring. Preference regarding blood test monitoring was the strongest of any medication attribute that we studied, accounting for 45% of the variation. Patients' decisions were also highly affected by the frequency of dosing (40% of the variation). Patients did not have strong preferences regarding the route of administration (15% of the variation). Understanding these patient preferences may lead to increased compliance with treatment plans and promote physician-patient partnership.