BACKGROUND: Medicaid covers a high-risk population typically underrepresented in clinical trial data and largely absent in observational studies of real-world cardiovascular risks associated with thiazolidinediones (TZDs), such as pioglitazone and rosiglitazone, which are used to manage type 2 diabetes. In November 2013, the FDA removed prescribing restrictions for rosiglitazone in light of new evidence that rosiglitazone did not increase the risk of heart attack compared with standard type 2 diabetes medications. Further investigation is needed to elucidate whether the risk of heart failure (HF) associated with TZDs may be exacerbated in the Medicaid population.