This study was designed to be an initial investigation of implicit models of illness, that is, the dimensional structure that organizes an individual's common-sense illness schema. Nurses, college students, and diabetics rated the qualities of two different diseases, one that was personally salient (i.e., flu or diabetes) and one with which they were familiar but did not have direct experience (i.e., cancer), on a 38-item Implicit Models of Illness Questionnaire (IMIQ). An exploratory factor analysis revealed a four-dimensional structure of illnesses composed of Seriousness, Personal Responsibility, Controllability, and Changeability. The stability of this four-dimensional model was established using confirmatory factor analysis to test the fit of this structure to the IMIQ data of another sample of subjects drawn from the same populations. The structure of this implicit model proved stable for judgments of different diseases and across groups of subjects, even though they differed in their physical-health status and occupational roles. The dimensions identified in the present study were compared to those described in other papers. Our dimensions seemed to be both personally and psychologically meaningful. The implications of this preliminary "generic" implicit illness model for future work in the field of health cognition are discussed.