Medication adherence is critical for cardiovascular disease prevention and control. Local health departments are well positioned to address adherence issues, however relevant baseline data and a mechanism for monitoring impact of interventions are lacking. We performed a retrospective analysis using New York State Medicaid claims from 2008 to 2009 to describe rates and predictors of adherence among New York City Medicaid participants with dyslipidemia, diabetes, or hypertension. Adherence was measured using the medication possession ratio, and multivariable logistic regression was used to assess factors related to adherence. Medication regimen adherence was 63%. Greater adherence was observed in those who were older, male, and taking medications from ≥3 drug classes. Compared with whites, blacks and Hispanics were less likely to be adherent (adjusted odds ratio [OR]=0.67, 95% confidence interval [CI]: 0.65-0.70 and adjusted OR=0.76, 95% CI: 0.73-0.78, respectively), while Asians were as likely. Medication adherence was inadequate and racial disparities were identified in NYC Medicaid participants on stable medication regimens for chronic disease. This study demonstrates a claims-based model that may be used by local health departments to monitor and evaluate efforts to improve adherence and reduce disparities.