Ochratoxin A is a mycotoxin produced by ubiquitous asporgili, mainly by aspergillus ochraceus and also by pencillium verrucosum. it is found all over the world in feed and human food and blood as well as in animal blood & tissue.The most treatening effect of (OTA) are its nephrotoxicity and carcinogenicity (Creppy et al., 1995).This study was performed in Egypt on 28 patients of chronic renal failure of unknown cause to detect the ochratoxin A in a serum by (ELISA) as a possible cause of these cases.