The purpose of the study was to analyze the changes in the quantity and qualitative composition of the lymphoid tissue of the walls of the rat's vaginal vestibule after a treatment course of naphthalan baths. The lymphoid formations of the walls of the vaginal vestibule of sexually mature female Wistar rats subjected to naphthalan baths were investigated. Obtained digital data were subjected to statistical processing. Morphological analysis showed that in the mucous membrane of the vaginal vestibule in rats of both experimental groups, as well as in the control, all forms of lymphoid tissue are present. Lymphoid formations of the vaginal vestibule are located near the initial parts of the glands. The lymphoid formations of the mucous membrane of the vaginal vestibule of rats do not actually change quantitatively and qualitatively after the course effect of freshwater baths, which indicates their safety. The treatment course of naphthalan baths causes an increase in the number of cells of the lymphoid tissue in all lymphoid formations, activation of lymphocytopoietic processes, a decrease in the level of cellular degeneration of lymphoid tissue.