Three 9α,11β-dihalo corticoids, 9α,11β-dichloro-17α,21-dihydroxy-Δ1,4- pregnadiene-3,20-dione-21-acetate, 9α,11β-dichloro-17α,21-dihydroxy-Δ4-pregnene- 3,20-dione-21-acetate, and 9α-bromo-11β-fluoro-17β:,21-dihydroxy-Δ1- pregnene-3,20-dione-21-acetate were studied by thymolytic, anti-inflammatory, and liver glycogen methods in the adrenalectomized rat. In all instances the substitution of the 11β-halo group for the 11β-hydroxy resulted in corticoids with significantly reduced activity.