The magnetic properties of Y(Fe 1 - x Co x ) 1 0 Si 2 compounds with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0 and YFe 8 M 2 Si 2 compounds with M = Fe, Ni, Co and Mn have been investigated. All investigated compounds are isotypical and crystallize in the ThMn 1 2 -type structure. The Co concentration dependence of the Curie temperature T C of Y(Fe 1 - x Co x ) 1 0 Si 2 compounds exhibits a maximum. Substitution of Mn for Fe leads to a distinct decrease of T C . Substitution of Ni for Fe has no remarkable influence on T C . The X-ray diffraction patterns of magnetically aligned samples show that the easy magnetization direction at room temperature is along the c-axis for all YFe 8 M 2 Si 2 compounds with M = Fe, Co, Ni and Mn. Substitution of Mn and Ni for Fe leads to a pronounced decrease of the anisotropy field, whereas substitution of Co for Fe has no remarkable influence on the anisotropy field. The anisotropy fields of YFe 8 Mn 2 Si 2 and YFe 8 Ni 2 Si 2 increase monotonously with decreasing temperature.