The purpose of the study. To study the features of the cellular immunity in patients with mechanical jaundice (MJ) of malignant genesis, depending on the level of bilirubin. Materials and methods. The study group included 50 patients with MJ of malignant genesis. The control group, consisting of 125 practically healthy volunteers, was comparable by sex and age with the group of patients examined. In the study of immune status, the method of indirect immunofluorescence of lymphocytes was used with monoclonal antibodies to CD3+, CD4+, CD8+, CD16+, CD19+, CD25+, CD95+, HLA-DR+. Statistical processing of data was carried out with the help of software packages Statistica for Windows 8.0 and Microsoft Excel, 2007 The critical level for checking statistical hypotheses was assumed to be p <0.05. Results. In patients with MJ of malignant genesis, the following features of the cellular immune system were presented: leukocyte count, leuko-T-cell, leuko-B-cell indices were increased, the number of lymphocytes, pan markers of T lymphocytes, T-helpers, cytotoxic lymphocytes, absolute amount of NK -cells, HLA-DR+ / CD19, CD4+ / CD8+ indices were decreased. When studying the characteristics of immunity, depending on the level of bilirubin, unidirectional disorders of the cellular immunity were detected. Conclusion. All patients developed secondary T-cell immunodeficiency, probably due to the combined effect of tumor, toxic and infectious factors. Only in patients with MJ with a level of bilirubin more than 200 μmol / l there were additional changes in the form of an increase in the relative amount of B lymphocytes and a decrease in the ratio of T-helpers to cytotoxic lymphocytes, due to a decrease in the former.