Background: Medication adherence for chronic medical illnesses has been studied extensively, but there is limited data evaluating medication adherence for comorbid medical illnesses in a psychiatric population. Furthermore, only one study has evaluated both medication adherence and clinical outcomes between the two populations. Examining medication adherence rates and clinical outcomes are important as chronic medical illnesses occur commonly in psychiatric patients, can be drug-induced, and have negative long-term consequences. Objectives: To compare antihyperlipidemic medication adherence and lipid control between individuals with psychotic disorders and those without a psychiatric illness. Methods: This was a retrospective medical record review of 124 subjects with hyperlipidemia and diabetes (62 subjects with schizophrenia or a related psychotic disorder and 62 randomly selected, age-matched individuals without a psychiatric illness) receiving medical and psychiatric care through the Veterans Affairs Medical Center during 2008. Cumulative mean gap ratio (CMGR) was used to determine adherence. Lipid values were utilized to compare lipid control between groups. Results: A significant difference in CMGR was detected. Subjects with psychotic disorders were without antihyperlipidemic therapy for 44 days compared with 62 days for the nonpsychiatric comparison group (P = 0.034). Antipsychotic adherent subjects (≥80% adherent) were more likely to adhere to their antihyperlipidemic medication (P = 0.0007). There were no significant differences between the groups for lipid control. Conclusion: Antihyperlipidemic medication adherence differed with the psychotic disorder group having fewer days without drug therapy. However, there was no significant difference in lipid control between subjects with a psychotic disorder and those without a psychiatric illness.