A study or the incidence of X chromosome loss from the mitotic complement of human ovary has demonstrated a small loss beginning between ages 36 and -15 years and increasing additively to age 75. This was earlier and less than has been shown for blood. In ovarian tissue, autosomal chromosomal loss declined with age while X loss increased. Though no correlation of X loss could be demonstrated with the clinical state of the menstrual cycle, there was a greater loss of all chromosomes in normally cycling subjects than in perimenopausal and postmenopausal subjects. The possibility that the menopause is initiated in the ovary is raised by findings of these correlates of aging.