The possibility that the luteotrophic effect of hysterectomy in the pseudopregnant rat is due to a decreased release of luteinizing hormone (LH) was investigated. The problem was approached indirectly by measuring pituitary LH concentration (Ovarian Ascorbic Acid Depletion Assay) (OAAD) in intact and hysterectomized pseudopregnant rats killed on various days of pseudopregnancy. Values obtained in the two groups were not significantly different. The size of the interstitial cells in the ovaries of the two groups of pseudopregnant rats was also not significantly different. The results do not offer support to the hypothesis that the uterus affects the secretion of LH, but rather suggest that it has a direct effect on the corpora lutea.