Background:Primary biliary cirrhosis (PBC)is rare chronic liver disease proceed with intrahepatic cholestasis.Histopatological changes in PBC are corresponding to chronic,nonpurulental destru- ctive cholangitis.In early stadium of PBC small and medium-sized bile ducts are affected,with progression of disease inflammation spreads to parenchyma and liver cirrhosis with symptoms of liver insufficiency develops. Met-enkephalin is pentapeptide belonging to opioid system. Changes in the opioid system were stated in the Alzheimer and Parkinson diseases,as well as in epilepsia,schizophrenia,manic syndromee,anxiety syndromee, alcoholism, neoplastic diseases, and in liver disorders.In the liver disorders,the concentration rates of opioid peptides in blood plasma and liver tissue are changed. The aim of the study was to answer the following question: Does met-enkephalin concentration in plasma and liver tissue corelate with histopatological changes in liver? Material/Methods: The study was carried out in 40 female patients with PBC.PBC has been found by means of biochemical,serological investigations as well as histopatological liver bioptates estimation.The patiens with different causes of liver disorders have been excluded.In each case,the percutaneus thick-needle liver biopsy was performed and a histopatological estimation was prepared.Histopatological changes of a liver tissue were estimated according to the Ludwig scale.Met-enkephalin concentration in plasma and liver tissue has been indicated in each patient.Results:According to the Ludwig scale results of histological examination have stated:17.5%patients with grade I,37.5%–grade II,35%–grade III,10%–grade IV.The patients were divided into 2 groups:the Group 1 included 22 female patients with grades I and II as pointed out in the Ludwig scale used, whereas the Group 2 (18 female patients)– grades III and IV.Statistically significant difference in met enkephalin concentration level in plasma and liver tissue has been indicated, along with the fibrosis and cirrhotic processes in the liver developing,the plasma met-enkephalin concentration rates increase,although the met-enkephalin content in the liver tissue decreases. For met-enkephalin plasma concentration p=0.0258 and for met-enkephalin liver tissue concentration p=0.0308. Conclusions:1.Along with the fibrosis and cirrhotic processes in the liver developing,the plasma met-enkephalin concentration rates increase,although the met-enkephalin content in the liver tissue decreases 2.Met-enkephalin concentration rate is an important and useful parameter that should be measured because it allows for the determination of the PBC disease progress/advancement in the organism of a patient.