Acicular &agr;‐FeOOH particles with particle length of about 0.2 &mgr;m and axial ratio of about 8 were used as the starting material to prepare acicular Fe‐Co alloy particles. They were made by adsorbing Co(OH)2on the surface of &agr;‐FeOOH particles, followed by dehydration, annealing, and reduction. In order to prevent sintering at high temperatures, the Co‐&agr;‐FeOOH particles were first dehydrated at 300 °C and then coated with a thin layer of silica before high‐temperature treatments. Furthermore, after reduction, the metallic powder was immersed in toluene to avoid oxidation. The particle structure of Fe‐Co was determined from x‐ray diffraction. It has been found that, up to 50 at. % Co, all the Fe‐Co particles have the same bcc structure and similar lattice constant. The magnetic properties of Fe‐Co alloy particles with different Co concentrations were investigated using a vibrating sample magnetometer. The specific saturation magnetizations &sgr;sare about 30% below those of bulk materials. The maximum value of &sgr;sat room temperature is obtained with 42 at. % Co. The coercivity that mainly originates from shape anisotropy is as high as 1250 Oe for the particles with 33 at. % Co. Furthermore, &sgr;sdrops sharply with Si content whileHcpeaks at 0.6% Si. The coercivities of the particles also depend on the crystallite size.Hcshows a maximum when the crystallite size is about 300 A˚.