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The size and function of the corpus luteum were examined after administration of luteinizing hormone releasing hormone antagonist. Luteinizing hormone releasing hormone antagonist was administered to three animal groups starting: 1) 2 days before the preovulatory luteinizing hormone surge inducing ovulation; 2) at initiation of the preovulatory surge; and 3) 2 days after the preovulatory surge. Although size and function of the corpus luteum were suppressed in all treated groups, the greatest developmental suppression occurred when luteinizing hormone release was blocked 2 days before the preovulatory surge of LH inducing ovulation. Therefore, optimal pregnancy rates in cattle may depend on pulsatile release of LH during the follicular phase of the estrous cycle in addition to that secreted during and after ovulation.