Direct reaction of hydroxy(2-pyridyl)methylphosphonic acid with zinc sulfate under hydrothermal conditions results in the formation of the novel heptanuclear cluster compound [Zn-7{(2-C5H4N)CH(OH)PO3}(6)(H2O)(6)]SO(4)center dot 4H(2)O (1). The inorganic core of the cluster can be described as a cylindrical drum made up of six Zn atoms bridged by six {CPO3} units that is centered by a seventh Zn atom. Crystal data: monoclinic, C2/c, a = 22.690(2) angstrom, b = 16.675(2) angstrom, c 18.151(2) angstrom, beta = 93.390(2)degrees.