AIM: The aim is to review about serum gamma Glutamyl transferase level in liver diseases. BACKGROUND: Serum Gamma glutamyl transferase is a membrane bound glycoproteins enzyme,which catalysts the transfer of the gamma glutamyl moiety of glutathione to various peptide acceptor. Gamma glutamyl transferase is present in hepatocytes and biliary epithelial cells, renal tubules, pancreas and intestine. Normal level of gamma glutamyl transferase is 9 - 85 u/L .GGT activity is widely used as a highly sensitive biochemical marker in the majority of malignant and non malignant liver diseases. Elevated GGT level of more than 10 times is observed in alcoholism and 2.3 times greater in non-alcoholic fatty acid liver disease. Some drugs and conditions interfere with GGT levels. GGT levels can be increased by alcohol phenytoin (Dilantin), an anti-seizure medication, and phenobarbitol, an antiseizure medication and sedative, and decreased by clofibrate, an anticholesterol drug, and birth control pills. OBJECTIVE: The objective of the review is to address the role of serum gamma glutamyl transferase activity in liver diseases. REASON: Serum gamma Glutamyl transferase also used as a bio marker for various liver disease. So it's necessary for the medical professionals to take serum GGT into account for diagnosis of liver disease.