The gamma-glutamyltransferase (EC 2.3.2.2) activity was measured in the blood serum obtained from 25 female patients with the uterine cervix carcinoma 10 and from 21 women with the uterine corpus carcinoma 10, treated by brachytherapy. The enzyme activity was determined in the five time points: before the brachytherapy, in the middle of the treating course, immediately after the application of the full dose of radium and in the seventh and the fourteenth day after the finishing the treatment. It was assumed the changes in the enzyme activity during the treatment course, and the highest values were observed immediately after the brachytherapy. It was noticed, that there is the direct connection between the enzyme activity changes and used brachytherapy method.