Although the asthmatic subject's compliance with a regimen of inhaled corticosteroids is often poor, it has been suggested this may improve during periods of increased severity. To test this, we measured daily peak expiratory flow rates (PEFRs), asthma symptoms, and the use of an albuterol inhaler over nine weeks period in ten patients with moderately severe asthma. The effect of changes in these severity indices on compliance with a q.i.d. regimen of inhaled beclomethasone was evaluated. The PEFR was measured in the morning before bronchodilator administration, and symptoms were graded on a scale of 4 to 16, while albuterol and beclomethasone inhalations were electronically recorded. Three measures of compliance with the beclomethasone regimen were used: (1) mean daily compliance ([number of inhalations/number of prescribed inhalations] x 100); (2) underuse, ie, the percentage of days with less than the prescribed number of inhalations; and (3) overuse, ie, the percentage of days with greater than the prescribed number of inhalations. Mean daily compliance was 67 +/- 36 percent, while underuse was observed in 69 percent and overuse in 11 percent of the days. Despite clinical exacerbations in six of the ten patients and considerable variation in the severity indices, no significant relationship was found between the change in asthma severity and compliance with the beclomethasone regimen. These findings do not support the concept of severity-modulated compliance with inhaled corticosteroids.