OBJECTIVES: We sought to define the characteristics of fluid retention after thiazolidinedione (TZD) initiation in patients with established heart failure (HF). BACKGROUND: Fluid retention associated with the use of TZD is commonly attributed to exacerbation of HF, which has led to the proscription of these potentially useful agents in patients with chronic HF. METHODS: We examined 111 consecutive diabetic patients with chronic systolic HF who were treated with TZD from January 1999 to June 2001. A retrospective chart review was performed to determine the incidence of fluid retention in this cohort. Physical signs of fluid retention were compared between TZD users and an age- and gender-matched control group of diabetic, non-TZD users with chronic HF who had fluid retention. Baseline clinical and echocardiographic data were compared between TZD users with and without fluid retention. RESULTS: Nineteen TZD users (17.1%) developed fluid retention, which reversed after drug withdrawal and presented predominantly as peripheral and not central edema. Comparing patients in the upper and lower tertiles of weight gain, more female patients and insulin users developed TZD-related fluid retention. However, there were no differences in the baseline New York Heart Association functional class or echocardiographic severity of cardiac dysfunction. CONCLUSIONS: Although fluid retention after treatment with TZD in diabetic patients with chronic systolic HF occurs, the mechanism is undefined. Fluid retention related to TZD tends to be peripheral and is usually reversible after drug withdrawal. No direct association between the risk of fluid retention and the baseline degree of severity of HF was observed.