Lay definitions of asthma were elicited through a single open-ended question from a population-based sample of mostly Puerto Rican, inner-city residents in Buffalo, New York. One hundred fifty-five household responses to the question, "What do you think asthma is?" were analyzed qualitatively using the editing approach. Five common codes emerged in order of significance: "symptoms," "disease," "triggers," "threat," and "coping." Overall, expressions of illness reflected a largely symptomatic perception of asthma regardless of asthma status. Perceptions of "disease" increased with higher level of education. Patients' definitions of illness should be considered to help reduce interpersonal barriers to asthma care.