The purpose of this study was to use a very simple self-report measure to identify patients who did not believe they were mentally ill and describe their characteristics. The study included 177 inpatients and outpatients with schizophrenia. Multivariate regression methods analyzed the relationship between illness belief and sociodemographic, clinical, and attitudinal factors. Thirty-seven percent of subjects did not believe they were mentally ill. Younger age, fewer depressive symptoms, lower perceived medication efficacy, greater satisfaction with current mental health, and less concern about mental illness stigma were associated with not believing one was mentally ill. Outpatients with fewer hospitalizations were less likely to believe they were ill. Inpatients with more hospitalizations were less likely to believe they were ill and had poor medication adherence. Readily identifying patients who do not believe they are mentally ill may be useful to clinicians and policymakers when matching at-risk patients with adherence interventions.