In a prospective study, we investigated the long-term compliance to fluticasone propionate (FP) by dry powder inhalation (Rotadisk) in subjects with early signs of asthma and chronic obstructive pulmonary disease (COPD) without an established diagnosis. Subjects were selected from a large screening program on early stages of asthma and COPD (Detection, Intervention, and Monitoring Program of COPD and Asthma [DIMCA] program) in the general practice. Forty-eight adult subjects with "early signs of COPD" (slightly increased forced expiratory volume in 1 sec [FEV1] decline of >0.04L/year) and 29 adult subjects with "early signs of asthma" (signs of bronchial hyperresponsiveness or reversibility) participated in a randomized placebo-controlled trial with FP (Flixotide 500 microg daily) versus placebo with a duration of 2 years or 1 year, respectively. Compliance was measured by counting Rotadisks returned. By means of a questionnaire, participants were asked about perceived effects and/or side effects of the trial drug. The mean overall individual compliance rates of 72% (range 7%-102%) in the early COPD trial and 71% (range 8%-99%) in the early asthma trial were maintained throughout the study. Perceived effectiveness (12% of the participants) or side effects (30% of the participants) of the trial drug were not related to compliance. The willingness of patients to use the trial drug in daily practice if efficacy would be proved was statistically significantly related to compliance during the trial (p = 0.017). It was concluded that the compliance rates found were relatively high in patients with symptoms of mild asthma or COPD without an established diagnosis. Conviction of the importance of treatment influenced compliance more positively than perceived (side) effects. These results again emphasize the importance of patient education in establishing early treatment with inhaled corticosteroids.