The immunohistochemical examination of 46 endometrial biopsies from women with chronic endometritis (CE) suffering from habitual abortions has found disturbance of correlations between various types of immunocompetent cells with domination of T-suppressors, increased accumulation of IgG on the surface of glandular epithelium. In CE, thickening of spiral arteries occurs not because of sclerosis but due to muscular hypertrophy, endometrial stromal-epithelial relations are impaired. Alterations in the distribution of the extracellular matrix components indicate defective endometrium maturation which may lead to inadequate oocyte implantation.