OBJECTIVES: To examine the association of antipsychotic adherence with adherence to medications for diabetes, hyperlipidemia, and hypertension and with healthcare utilization. METHODS: Medstat Medicaid claims data were used to generate cohorts of patients with schizophrenia newly initiating a second generation antipsychotic and using medications for diabetes, hypertension, and hyperlipidemia.  Quarterly (Q) adherence measurements were calculated for each patient to capture initiation (Q1), continuation (Q2-Q4), and maintenance (Q5-Q8) periods via the proportion of days covered (PDC) > 80%.  Generalized estimating equations examined the association of initiation period antipsychotic adherence with comorbid medication adherence and health service utilization during the continuation phase.  Similarly, continuation phase antipsychotic adherence was used to predict parallel maintenance phase outcomes. RESULTS: Patients adherent to antipsychotic treatment during initiation (Q1) were more adherent to medications for diabetes [Odds Ratio (OR) = 1.77; 95% CI(0.95, 3.29)], hypertension [1.36, (0.91, 2.04)], and hyperlipidemia [2.24, (1.02, 4.90)] during the continuation phase.  Similarly, continuation phase antipsychotic adherence was associated with higher adherence to medications for diabetes [4.99, (2.85, 8.71)], hypertension [7.51, (5.07, 11.12)], and hyperlipidemia [5.68, (2.71, 11.92)] during the maintenance phase.  Higher antipsychotic adherence during the continuation phase also was associated with more frequent outpatient visits [Incident Rate Ratio = 1.53 (1.21, 1.94), 1.57 (1.35, 1.82), 1.63 (1.28, 2.07)], less frequent inpatient admission [OR = 0.73 (0.43, 1.26), 0.70 (0.49, 1.00), 0.87 (0.49, 1.54)] and less frequent emergency department use [OR = 0.68 (0.42, 1.10), 0.58 (0.47, 0.78), 0.76 (0.47, 1.25)] during the maintenance phase among patients with diabetes, hypertension, and hyperlipidemia respectively. CONCLUSIONS: Antipsychotic adherence was associated with better adherence to medications for chronic comorbid health conditions as well as a trend toward lower inpatient and emergency department use over a 2 year period.  These findings suggest potential benefits to antipsychotic adherence beyond mental health management.