Cytological characteristics and pattern of distribution of different cell types in the epithelia of cervix and uterus of crab-eating macaque (Macaca fascicularis) in follicular and luteal phases of the menstrual cycle and amenorrhea were studied. The cervix uteri and uterus exhibit remarkable structural differences in the ciliated, secretory, and ciliated-secretory cells. Since the number of ciliated-secretory cells in the uterus is higher than in the cervix, it is believed that they form an additional source for the secretion of uterine fluid during the menstrual cycle. Both ciliated and secretory cells undergo degeneration ; extensive cytoplasmic vacuolation associated with pycnosis and disorganization of the nuclei are encountered.