In sheep, placental size is maximal by midgestation, but blood flow continues to increase until term. No nerves are present and ANG II is thought to be a major regulator of vascular tone. We hypothesized that angiotensin type 2 receptors (AT₂) would predominate over type 1 (AT₁) until late in gestation and be primarily expressed in the vasculature. Real-time PCR, hybridization histochemistry, and ligand-binding studies were performed on placentae and fetal membranes at 27, 45, 66 ± 1, 100 ± 4, 130, and 140 days of gestation (term  150 days) to determine quantitative changes and localization. The maximum level of AT₁ expression occurred in the 45-day placenta and was located predominantly in the maternal stromal cells. AT₁ receptors were expressed in the endothelial cells of the chorion in the first half of pregnancy, where later in gestation, both AT₁ and AT₂ receptors were predominant in blood vessels. These results suggest that ANG II, via the AT₁ receptor, may have hitherto unsuspected important roles in the growth/function on the ovine placenta during the maximal growth phase.