Lymphoid formations of human endometrium are presented in stroma of the uterine corpus mucous membrane as lymphoid cells (so called diffuse lymphoid tissue), lymphoid nodules and interepithelial lymphocytes in glandular and covering epithelium++. Peculiarities in organization of these formations are seen as slight saturation of the endometrium with lymphoid tissue, small size of lymphoid nodules++. The lymphoid structures in question reach their maximal development during the adolescent and first mature age. During the generative period among diffusely arranged T-lymphocytes sub-populations of T-suppressors predominate. This is probably connected with participation of suppressive mechanisms of local immunity in ensuring blastocyst implantation.