The paper gives data on the nature of changes in two markers CA 125 and HE4 in 12 patients with ovarian cancer (OC) during their treatment and follow-up to assess whether it is expedient to supplement laboratory CA 125 monitoring with the second marker. The more marked changes in one marker (versus the other) suggested: a) its higher baseline level (as related to the upper normal range); b) a greater reduction rate of during effective treatment); c) earlier onset, a higher rate of its increase and to higher values in the development of recurrent disease. In most cases, the changes in the level of both markers correlated with treatment response and clinical course. In 8 patients, the time course of changes in CA125 during both treatment and recurrence turned out to be more pronounced than that in HE4 and in 3 patients, HE4 had clear advantages over CA 125. The findings suggest that in a number of cases, HE4 is likely to give additional information on the dynamics of a tumor process in OC.