The earlier experimental investigations utilizing a mouse model have demonstrated the importance of certain native factors responsible for the natural protection of vaginal phagocytic cells, such as activity of lysocomal proteolytic enzyme cathepsin D and the capacity for phagocytosis. The present study using cells contained in the vaginal lavage from healthy women showed that their phagocytic activity remained virtually unaltered with time whereas variations of cathepsin D activity significantly correlated with the dynamics of serum estrogen/progesterone activity during the menstrual cycle. It should be emphasized that the high-estrogen and high-progesterone phases of the cycle were characterized by the high and low level of enzymatic activity, respectively. In contrast, the cathepsin D activity underwent a sharp rise in women presenting with certain infectious and non-infectious diseases of the reproductive system. The results of the present study indicate that the level of cathepsin D activity in vaginal phagocytic cells can be a valuable marker of the degree of protection of mucosa in the women's urogenital tract.