OBJECTIVES: The ability of asthma patients to feel their maintenance inhaler work right away and their satisfaction with this perception could serve as positive reinforcement of daily inhaler therapy, leading to higher levels of persistence and improved health status. This study examined the reliability and validity of a 5-item weekly diary, the “Onset of Effect Questionnaire” (OEQ), for describing patient perceptions associated with feeling a maintenance therapy working right away as an initial step in understanding this phenomenon. METHODS: Secondary analyses of data from 360 patients (aged >18 yrs) with mild to moderate asthma gathered during a Phase III, 12-week, randomized, double-blind, double-dummy, placebo-controlled clinical trial (SD-039-0716) comparing budesonide/formoterol pMDI with its monoproducts. OEQ items were analyzed using dichotomous scaling; the items identifying patients who perceived their medication working right away (perception) and patients satisfied with this perception (satisfaction) at Week1 were pre-specified as primary outcomes. Statistical tests of reproducibility and validity were based on a comprehensive, a priori analysis plan. RESULTS: One-week reproducibility: perception: phi=0.77; satisfaction: 0.70 (p<0.0001). Construct validity: both perceiving and satisfied patients exhibited a higher increase in FEV1 15 minutes post-baseline than those who were not (p<0.0001). Those perceiving and satisfied patients also reported higher symptom severity scores (Asthma Quality of Life Questionnaire) than those who were not (p<0.05; p<0.01), with no difference in rescue medication use. Predictive: Patients perceiving and those satisfied at Week 1 had higher 15 minute post-dose FEV1 (p<0.0001) and greater satisfaction with medication (Overall Perception of Medication subscale of the Patient Satisfaction with Asthma Medication (PSAM) questionnaire) and asthma relief (PSAM Relief subscale) at the end of Week 2 than patients who did not (p<0.0001). CONCLUSION: The weekly diary approach is a reliable and valid method for identifying patients who perceive their medication working right away and those satisfied with this perception.