Portal hypertension leads to formation of portosystemic collateral veins which are discovered by endoscopy.Because of complications of endoscopy,we try in this study to find good indicator for portosystemic collateral veins to decrease unnecessary use of endoscopy,this indicator is blood ammonia levels.This would encourage the use of endoscopy screening in this at risk population only, and increase the physicians’ surveillance for ascites and/or PSE.So, we study the relationship between blood ammonia levels and presence of portosystemic collateral veins in 40 patients with liver cirrhosis.We measure venous ammonia concentrations by enzymatic method .in our results,we find correlation between ammonia levels and presence of portosystemic collateral veins as esophageal varices and anorectal varices.But, we should take care in the collection, handling, storage, and analysis of blood samples to decrease degree of error in ammonia levels.