To study the time of ovulation in the menstrual cycle, an investigation was planned to recover ova from the uterine tubes, to correlate their condition with the menstrual history and stage of development of the early corpora lutea from which these ova had been extruded, and to quantitatively analyze the ovarian hormone level in tissues of the human ovary. The preliminary report records the recovery of 7 ova from the uterine tubes. 1 case involved twin ova where each ovary contained an early corpus luteum. Another involved internal migration of the ovum from the left ovary to the right tube. One ova was recovered on the 12th, 4 on the 15th, and 2 on the 16th day of the menstrual cycle. The last 2 showed signs of degeneration. The corpora lutea of each ova were examined and described. The ova, uterine tubes, corpora lutea, and some endometrium are being prepared for histologic st udy. A series of analyses of hormone content of human ovarian tissues is also being accumulated.