['Injections of estradiol-17 beta (E2) are known to both induce anovulation and alter lymphocyte maturation in female mice. The current study examined whether the two events are related.', 'Female (C3H/HeJ x 129J)F1 (C31) mice were injected with 20 micrograms of E2 from 0-3 days, or from 3-6 days, postpartum. At 8, 12, 20, 32, or 40 weeks of age, the animals were killed, T lymphocytes were characterized, and ovaries were histologically examined for the presence of corpora lutea.', 'Animals injected with E2 from 0-3 days postpartum had percentages of CD8+ thymocytes and CD8+ splenocytes that were always lower than in noninjected females, and the E2-injected animals never ovulated, even by 40 weeks of age. In contrast, animals injected with E2 from 3-6 days of age had percentages of CD8+ thymocytes and CD8+ splenocytes that, although initially lower than in control females, attained control values by 32 weeks of age. In addition, at 32 weeks of age a number of the 3-6-day E2-injected females ovulated, whereas at earlier ages none had. Further, injections of E2 had little effect on the percentages of CD4+ thymocytes and splenocytes in these animals.'] Is the anovulation in female mice resulting from postnatal injections of estrogen correlated with altered levels of CD8+ lymphocytes?