Nonadherence with asthma medications is a significant problem associated with unnecessary functional limitations. The development of measures to assess psychological factors important to adherence with medication regimens among adult patients with asthma is described in the present report. The results indicated that the reliability and validity of the newly designed measures were adequate. Patients that did not perceive a need to take their medications as prescribed or those already taking their medications as prescribed had better pulmonary function. The results are discussed in terms of their implications for future studies, such as motivational interventions to enhance adherence with asthma medications.