Purpose of investigation: Since leptin is believed to be a key player in carcinogenesis, a study has been designed to investigate the relationship between leptin levels and endometrial cancer. Methods: A study including 30 patients with endometrial cancer and 30 healthy controls was carried out between November 2008 and July 2009 in Hacettepe University Hospital. All patients with endometrial cancer underwent a complete surgical staging procedure including lymphadenectomy. Preoperative leptin levels of endometrial cancer patients and healthy controls were compared. The relationships between leptin levels and stage, grade, histological type and lymph node status of endometrial cancer cases were evaluated. Results: The mean serum leptin levels were 16.9 ng/ml among endometrial cancer cases and 19.0 ng/ml among controls (p = 0.32). Of endometrial cancer cases, the mean leptin level was found to be 15.8 ng/ml for Stage I and 18.5 ng/ml for Stage II-IV disease (p = 0.34). The figure was 17.7 ng/ml for endometrioid and 13.2 ng/ml for non-endometrioid type of tumor (p = 0.24). The mean leptin levels of 16.3 ng/ml for grade 1 and 19.9 ng/ml for grade 2-3 tumors were observed (p = 0.07). The cases with positive and negative lymph nodes had leptin levels of 20.2 ng/ml and 16.1 ng/ml, respectively (p = 0.30). Conclusions: Serum leptin levels in endometrial cancer patients were similar to healthy controls. Leptin did not show any significant correlation with stage, grade, histological type and node metastases in endometrial cancer.