Daily inhaled bronchodilator medication usage was recorded using an electronic device and airway obstruction by daily peak flow measurement. The demographic, clinical, and psychological characteristics of the subjects were noted. Subjects were allocated to as-needed (prn) medication usage groups according to the mean number of inhaler activations on days with zero, moderate, and severe airway obstruction. Segregation into arbitrary and nonarbitrary use, and into overuse, appropriate use, and underuse resulted in six usage groups. Appropriate use was observed in only 10 of 39 subjects. The major psychological variable to differ among groups was the MMPI variable Pt, representing general anxiety. Arbitrary users had a significantly higher mean score than nonarbitrary users. The variable Specific Internal Awareness, representing a perceived difficulty in recognizing the premonitory symptoms of an asthma attack, also differed among the usage groups, with arbitrary users having the lowest scores. These findings raise the possibility that reliance on an objective measurement of airway obstruction rather than on subjective symptomatology might enhance compliance with prn medication in some patients.