Ovarian angiotensin II (Ang II) receptors display a cyclical pattern of variation during the rat estrous cycle. Ang II receptors, estimated by the specific binding of the Ang II receptor antagonist [^125Iiodo-[Sar^llle⁸] Ang II to ovarian membranes, were lowest at estrus [binding site density (B_max = 35 ± 2 fmol/mg; binding site affinity (K_D) = 2.0 ± 0.2 nM] and highest at diestrus I (B_max = 59 ± 3 fmol/mg; KD = 1.6 ± 0.1 nM). We have previously shown that Ang II receptors in the rat ovary predominantly exist on the granulosa cell layer of a subpopulation of follicles. Our present studies show that the Ang II receptor-containing follicles in the rat ovary are mainly atretic (-80%) or show signs of early atresia (-15%) during all stages of the estrous cycle. A small number of Ang II receptor-containing follicles were healthy (-5%). In contrast to the Ang II receptor-containing follicles, the FSH receptor-containing follicles were predominantly healthy (<90%). Follicles which contained both Ang II receptors and FSH receptors were mainly early atretic. Since Ang II receptor-containing follicles in the rat ovary were mainly atretic these studies suggest that in the rat Ang II may be a major factor in regulating the function of atretic ovarian follicles. (Endocrinology122: 2727–2734, 1988)