||In this paper, we present a theoretical study of magnetic properties of MPo (M=Ti, V, Cr, Mn, Fe) compounds in the zinc-blend structure using full-potential linear augmented plane wave method. Our calculation indicates that MnPo and FePo are antiferromagnetic, whereas TiPo, VPo, and CrPo are magnetic. The ferromagnetic phase is enhanced with decreasing lattice constant and increasing atomic number along the sequence TiPo-->VPo-->CrPo. TiPo, VPo, and CrPo are predicted to be half-metal ferromagnetic with magnetic moments of 2.0µB, 3.0µB, and 4.0µB, respectively, which is confirmed from the calculated minority (majority) spin channel band structure showing the semiconducting (metallic) behavior of these compounds. The magnetism comes essentially from the d orbital of Ti, V, and Cr atoms. In addition, we have found that half-metallicity can be maintained even when spin-orbit interaction is included for TiPo and VPo. However spin-orbit effect destroys magnetism in CrPo.