The paper is aimed at evaluation of certain indices of cellular immunity in pregnant women with gestosis superimposing pre-existing renal diseases and comparing them with the immunological condition of women with essential gestosis. T lymphocyte subpopulations and lymphocyte proliferative responses to mitogens (phytohemagglutinin--PHA, concanavalin A--Con A and pokeweed mitogen--PWM) in the fetal calf serum and autological sera were studied. The groups of examined pregnant women in the 3rd trimester did not vary with regard to gestation age, calendar age and to the severity of edema (E), proteinuria (P) and hypertension (H) gestosis symptoms. It has been found that equal changes occur in both groups of women, regarding the examined indices of cellular immunity, when referred to normal pregnant women. In the gestotic women a decreased absolute and percentage content of CD8+ T cells and increased percentage of CD3+ and CD4+ lymphocytes were found in comparison with the normal pregnant women, which led to an almost 2.5-fold increase of CD4+/CD8+ ratio. The sera of gestotic women, in comparison with the healthy pregnant group, strongly increased the proliferation of Con A and PWM-induced lymphocytes. It may then be assumed that the observed immunological changes do not coincide with the primary causes of gestosis. We suggest that immunological factors largely contribute to the development of essential gestosis and gestosis superimposing pre-existing renal disease.