213 Background: The presence and the impact of metabolic syndrome (MS) in castration-resistant prostate cancer (CRPC) men treated with novel hormonal therapies, as abiraterone, has not still been studied. The study aims to assess the impact of MS on progression free survival (PFS) and overall survival (OS) from time starting abiraterone. Methods: We retrospectively evaluated a consecutive series of metastatic CRPC patients treated with abiraterone after docetaxel failure. MS, as defined by modified Adult Treatment Panel (ATP) III criteria, was assessed at the time of initiation of abiraterone, during treatment and follow-up. Cox regression model was used to evaluate the role of MS on the two end-points. Results: One hundred seventy eight patients had sufficient data to assess the presence of MS. Mean age (± SD) at start of abiraterone was 74.0 ± 7.7 years. Seventy out of 178 patients (39.5%) met MS criteria at baseline, before abiraterone initiation, whereas for eleven patients this occurred during treatment. Median PFS was equal to 5 months for patients with MS versus 9 months for those without MS. Patients with MS had a 2-fold increased risk of progression or death for all causes than patients without MS (HR=1.9, 95% CI [1.3-2.7], P<0.001). Median OS was 16 months and 22 months in patients with and without MS, respectively. After adjusting for covariates, MS resulted not significantly associated to OS (HR=1.2, 95% CI [0.8-1.9], P=0.340). Conclusions: MS may represent a complication of patients treated with abiraterone. The presence of MS appears to be a risk factor for shorter PFS in patients with CRPC treated with abiraterone, even if it does not show any impact on OS, so it needs a further prospective evaluation.