Certain conjugated biliary acids (total pool - choliglycine - sulpholytic choliglycine) and the following haematochemical parameters: total bilirubin and its direct quota, alkaline phosphatase, albumin, prothrombin activity, gamma globulin, oxalacetic and pyruvic transaminase were radioimmunologically (RIA) studied in 115 subjects. Subjects were divided into the following subgroups: --20 normal controls; --20 cases of persistent chronic hepatitis; --20 cases of active chronic hepatitis; --15 cases of A.C.H. with cirrhosis; --20 cases of cirrhosis without direct hyperbilirubinaemia; --20 cases of cirrhosis with direct hyperbilirubinaemia. Each case was assigned to its particular group on the basis of the histological report on each patient. The following observations were drawn from the results obtained: --there is a progressive increase in above normal biliary acid rate in proportion to the gravity of the liver pathology; --choliglycine especially and to a lesser extent the total pool increased sufficiently to distinguish between normal and hepatopathic subjects (PCH and ACH) and also between PCH and ACH patients; --the combination of cirrhosis and ACH causes a significant increase in total pool and chliglycine over levels noted in ACH alone; --in contrast no difference is found between the levels of these acids in inactive (or minimally active) cirrhosis and ACH with cirrhosis; --gamma globulin, oxalacetic and pyruvic transaminase levels were found to have substantially the same diagnostic significance as choliglycine in the early stages of liver diseases. Significant correlations were also encountered between total conjugated biliary acid pool and choliglycine (not in the group with cirrhosis without direct hyperbilirubinaemia) and between total pool and choliglycine with haematochemical cholestasis test results (alkaline phosphatase and total and direct bilirubin) the latter only in the two cirrhotics groups. In conclusion, choliglycine was found to be the most sensitive of the biliary acids routinely measured by RIA and is valuable in clinical practice not as a substitute for the main liver tests but as an extremely useful and sensitive addition to them. In clinical practice, its use is recommended in the diagnosis and monitoring of healthy subjects at risk and those with chronic liver conditions (PCH, ACH, ACH + C).