Abstract: We report on the latest progress of half-metallic ferromagnetic materials compatible with III-V and II-VI semiconductors, which are believed to play key roles in spintronic devices. Using an accurate first-principle density-functional method we find that three of the 3d-transition-metal chalcogenides are excellent half-metallic ferromagnets and would be fabricated as thin film or layer materials with a thickness large enough for future spintronic devices at the nanometer scale.