Remarkable changes in vascular permeability and neovascularization occur within the ovulatory, luteinizing follicle. To evaluate the importance of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) in periovulatory events, sequential experiments were designed in which vehicle (PBS/0.1% BSA; controls, n = 13) or a low dose (1.5 μg; n = 4) or a high dose (7.5 μg; n = 4) of a VEGF antagonist, soluble VEGF receptor 1 (sVEGFR1) chimera, was injected directly into the preovulatory follicle of rhesus monkeys the day before (Day −1) or the day of (Day 0) the midcycle LH surge during spontaneous menstrual cycles. After vehicle injection, animals typically exhibited patterns and levels of serum progesterone (P₄) that were comparable to those of untreated animals in our colony. Following low-dose sVEGFR1 injection, serum P₄ levels were diminished in two of four animals from the early to midluteal phase, but were similar to vehicle controls thereafter. In contrast, high-dose sVEGFR1 injection decreased serum P₄ levels throughout the luteal phase compared with levels in controls (P < 0.05), but it did not cause premature menstruation. Control follicles displayed indices of rupture (protruding stigmata) and luteinization. However, sVEGFR1-injected follicles exhibited signs of distension (torn surface epithelium/tunica albuginea) and luteinization, but not necessarily timely ovulation. Histological evaluation of serial sections from ovaries removed on Day 3 after treatment revealed that all (n = 3) vehicle-injected follicles ovulated, whereas half (n = 3 of 6) the sVEGFR1-injected follicles failed to ovulate and still contained an oocyte in the antrum. No appreciable differences were apparent between treatment groups in numbers of cells in luteal tissue (Day 3 or 6 after treatment) that stained positive for immunochemical or histochemical markers of proliferative (Ki67), endothelial (platelet endothelial cell adhesion molecule 1), and steroidogenic (3β-hydroxysteroid dehydrogenase) cells. However, there was a dose-dependent increase (P < 0.05) in extracellular space in the corpus luteum by midluteal phase in sVEGFR1-treated animals. The data suggest that acute exposure to a VEGF antagonist can impair ovulation, and the subsequent development and functional capacity of the primate corpus luteum. The results are consistent with a critical role for VEGF in normal ovarian function during the periovulatory interval in primates.