Individuals with serious mental illness (SMI) experience significant premature mortality due to somatic conditions but often receive sub-optimal somatic care, but little research has been done to understand how general medical clinicians' attitudes may affect care provision or health outcomes. This review describes general medical clinicians' attitudes toward people with SMI, compares these attitudes to attitudes among mental health clinicians or toward individuals without SMI, and examines the relationship between attitudes and clinical decision making. Seventeen studies were reviewed. General medical clinicians reported negative attitudes toward individuals with SMI. These attitudes were generally more negative than attitudes among mental health clinicians and were consistently more negative when compared to attitudes toward individuals without SMI. Four studies suggest that these negative attitudes have an adverse effect on clinician decision making.