OBJECTIVE: Describe relationships between changes in work outcomes (WO) and changes in asthma severity over a one-year period. METHODS: This longitudinal study surveyed adults enrolled in a managed care organization using identical mailed surveys. 106 respondents completed both the 1997 and 1998 questionnaires and reported working outside the home. Self-reported WO included missed work days due to asthma and work performance (WP) from the Functional Status Questionnaire, a 6-item scale using a 4-point Likert scale, transformed to a 100 point scale. A 4-week time reference was used. Perceived severity was determined by asking patients their perceived severity on a 5-point scale from very mild to very severe; evaluated severity was based on reported symptoms matched to national guidelines. Respondents were grouped by change in asthma severity: improvement; no change; or decline of at least one severity category. Analysis included descriptive statistics, paired Student’s t-test, and McNemer’s test. RESULTS: Initially, respondents’ mean age was 44.4 (+10.9) years; 72 (68.6%) were female; 76.7% had an annual family income of >$40,000; 96.2% were Caucasian; and 76.4% had some college education or more; 42.9% perceived their asthma severity as very mild or mild, 38.1% moderate, and 19.1% as severe or very severe. Based on symptoms, 32.4% were classified as intermittent mild, 28.6% mild persistent, 36.2% moderate, and 2.9% severe asthma. WP scores changed in the expected direction based on changes in asthma severity: no change in perceived severity (n=58) had no significant change in WP score (91.3+13.0 versus 92.9+12.4, p=0.52); improvement in perceived severity (less severe, n=17) had improved WP scores (91.8+7.9 versus 94.4+9.4, p=0.30); and worsening of perceived severity (n=26) had a decline in WP score (94.4+8 versus 91.3+10.9, p=0.07). WP score trends were similar based on evaluated severity. There were no significant differences in changes in the number of respondents who reported missing work. CONCLUSIONS: Changes in WP are related to asthma severity. The measure of missed days work is less consistently related.