To determine the suitability of serum endocan (ESM-1) levels for diagnosing and monitoring renal cell carcinoma (RCC), we measure serum ESM-1 levels in 56 RCC patients who had undergone radical or partial nephrectomies and 56 age- and sex-matched healthy kidney donors. The gene discussed is ESM1; the disease is hereditary clear cell renal cell carcinoma.