Angiogenesis is essential for normal growth and function of the corpus luteum. The roles of various angiogenic factors in these events are being elucidated. Endocrine gland vascular endothelial growth factor (EG-VEGF) has recently been described in the human ovary. To define the localization of EG-VEGF mRNA in the corpus luteum and determine changes in its expression, dated human corpora lutea were studied at the early, mid-, and late luteal phases. Quantitative RT-PCR was employed to determine changes in EG-VEGF mRNA and compare expression to its related factor prokineticin-2 and the established angiogenic factor, VEGF. In situ hybridization was used to localize sites of production of EG-VEGF. To investigate whether expression of EG-VEGF was under the influence of LH or progesterone, luteinized granulosa cells were stimulated with human chorionic gonadotropin in the presence or absence of a progesterone synthesis inhibitor. EG-VEGF mRNA increased throughout the luteal phase, whereas there was no change in VEGF mRNA. The relative abundance of RNAs based upon PCR signal intensity showed that VEGF and EG-VEGF were highly expressed, whereas expression of prokineticin-2 was low. EG-VEGF mRNA was localized predominantly to granulosa-derived cells of the corpus luteum. Human chorionic gonadotropin stimulated both VEGF and EG-VEGF mRNA in vitro, but the level of expression was not influenced by progesterone. These results establish that in the human corpus luteum EG-VEGF is principally derived from granulosa lutein cells and that its synthesis is highest during the mid- to late luteal phase.