The time required for 249 supravitally stained donor eggs to pass through the ampullae of the oviducts has been determined for 31 rabbits arranged in six groups as follows: 45 ova in eight normal rabbits in estrus, mean transport time 9.4 ± 1.6 mm (SD) (number of rabbits used as n for determination of SD); 56 ova in seven normal estrous rabbits 10–15 hr after an ovulation-inducing injection of HCG, mean transport time 6.1 ± 1.5 min; 43 ova in five normal estrous rabbits 12–14 hr after an injection of 20α-OH-progesterone, mean transport time 4.2 ± 0.5 min; 31 ova in four normal estrous rabbits 12–14 hr after an injection of progesterone, mean transport time 4.3 ± 1.0 min; 45 ova in four normal estrous rabbits 19–20 hr after ovariectomy, mean transport time 3.7 ± 0.5 min; 29 ova in three normal estrous rabbits 12–14 hr after injection of an estrogen antagonist (CN-55, 945–27), mean transport time 4.3 ± 1.7 min. The mean ovum transport time was significantly longer (p < 0.01) in the rabbits in estrus than in any of the other groups. Ampullary muscle contractions were more coordinated and vigorous in rabbits at the time of a gonadotrophin-induced ovulation or after progestin injection than in unstimulated does in estrus. Muscle contractions 19–20 hr after ovariectomy and 12–14 hr after injection of a synthetic estrogen antagonist, CN-55, 945–27, were as vigorous as those observed at the time of ovulation and after progestin injections in normal estrous rabbits, but, in general, the contractions were not as well programmed as contractions which occur at ovulation in the normal animal. Muscle contractility of the ampulla was minimal, and the egg transport was slower in normal, unstimulated, estrous rabbits at a time when estrogens in the plasma and target tissues are presumed to be at a relatively high level. There is an increasing body of data indicating a significant increase in the secretion of progestins in the ovaries as ovulation approaches. We suggest that the increase in vigor and orderly programming of muscle contraction as well as the acceleration of egg transport at the time of ovulation may be related to an increase in the secretion of progestins and a fall in the level of estrogens.