The frequency and magnitude of hepatotoxic reactions were compared in 147 new cases of pulmonary tuberculosis within the first three months of chemotherapy (CT) by standard regimen 1 [H, R, Z, S (E)] (Group 1) and regimen 2B [the same drugs + kanamycin (amikacin) and fluoroquinolones] (Group 2). Their efficiency was evaluated from 6 serum indices--the level of bilirubin, the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AP), and gamma-glutamyl transpeptidase (GGTP), and thymol test results. Tests were monthly carried out. The results were separately analyzed in patients with and without baseline abnormalities in the indices being tested. Within the first two months of CT, the patients without baseline abnormalities showed the slightly higher frequency and magnitude of hepatotoxic reactions on receiving regimen 2B. Following 3 months of CT combined with hepatoprotectors, the patients treated by standard regimen 1 had solitary laboratory signs of hepatic damage, but there was a regular elevation of GGTP in the regimen 2B group. After a month of regimen 1 CT in combination with hepatoprotectors, the patients with baseline abnormalities has positive changes in all the studied indices. In the patients treated by regimen 2B in combination with hepatoprotectors, the changes were the same, except for GGTP that remained to be at the increased baseline levels. Following 2 months of CT, in Group 1 positive changes continued in the studied markers and, with regimen 2B treatment, abnormal changes began increasing again. After 3 months abnormal changes were single in the markers of hepatic damage with regimen 1 treatment and there was a repeated significant rise in the values of AP and GGTP with regimen 2B. It is concluded that in addition to ALT and AST, GGTP is of great informative value in controlling the hepatotoxic effects of CT.