A sulfate-bridged tetracosanuclear manganese cluster, (Et3NH)(2)[{Mn-8(L)(4)(mu(4)-O)(2)(SO4)(2)(H2O)(3)}(3)(SO4)] (1) (H3L = N-(2-hydroxyethyl)-2-hydroxybenzylideneimine-3-carboxylic acid) was synthesized by the reaction of a Schiff-base ligand H3L and manganese acetate in the presence of sulfuric acid. The tetracosanuclear manganese cluster is composed of three octanuclear manganese units, which include four ligands, two mu(4)-oxo ions, and two capping sulfate ions. The cluster shows antiferromagnetic interactions between the manganese ions.