Data were collected from three samples using the Implicit Models of Illness Questionnaire (IMIQ) to assess illness representations as described in the self-regulation model of common sense illness representations. A factor structure was identified which displayed some similarities to the common sense model. This structure was used to examine illness representations of students and patients concerning three illnesses-rheumatoid arthritis (RA), multiple sclerosis (MS), and human immunodeficiency virus (HIV). Representations differed across illnesses and respondent status (patient vs. student). Students rated individuals as having more personal responsibility for RA or MS than did patients; moreover, the difference between patient/student ratings was greater with respect to MS than it was for RA. Patients were more aware of the variable nature of RA and MS symptoms than were students. This study demonstrates the value of the IMIQ as a tool for assessing illness cognitions and suggests that illness representations differ as a function of personal experience and personal relevance.