Characteristics of subjective symptomatology of asthma were examined within a group of 132 adult asthma patients receiving medical care in a university-based, ambulatory clinic setting. Patients responded to 36 symptom descriptions or adjectives associated with asthma which were included in a modified version of the Asthma Symptoms Checklist (ASC). A principal components exploratory factor analysis was conducted and five factors were identified. The five factors measured 1) panic-fear, 2) airways obstruction, 3) hyperventilation, 4) fatigue, and 5) irritability. Psychometric properties of the factor scores were satisfactory. The reliabilities were high, standard deviations were large, and differences in factor mean scores conformed to clinical experience. Correlational analyses support the construct validity of the ASC, especially the panic-fear factor. An important outcome of this study was to verify the ASC factor structure in an outpatient setting. The ASC was confirmed as a valuable instrument for use in self-management programs for adults with asthma. The five ASC factors represent highly stable components of subjective symptomatology of asthma among diverse adult patient populations and geographical settings.