This study measured the relative contribution of four cues: symptoms, effect on activities, emotions and social life, to patients' judgments of overall asthma severity. Judgement analysis techniques were applied to patients' assessments of overall asthma severity using asthma states described in scenarios based on these cues. Altogether, 40 patients, mean age 52 yrs, mean forced expiratory volume in one second 67% predicted, were studied. The relative importance of the cues varied widely between patients; symptoms contributed to 47% of the judgment of asthma severity (range 15-86%), activities 19% (1-73%), emotions 14% (0-43%), and social life 19% (2-57%). Some patients had difficulty with the judgment task, they tended to be older or have worse health. A total of 21 patients had consistent judgment policies. Cluster analysis identified two policy types. In one, symptoms were weighted heavily, in the other all cues were weighted similarly. Policies were not related to disease or demographic factors. Symptoms are important cues for patients when assessing asthma severity, but other cues may be more important in some patients. Patients fall into two groups: those who rely on symptoms and those who use several cues.