Mössbauer and magnetic measurements were carried out on the compositions Mn 4.5Fe 0.5Ge 3, Mn 4FeGe 3, and Mn 3.5Fe 1.5Ge 3. Data were obtained from liquid N 2 to about 600°K. The iron substitution takes place initially in the 4( d) sites of the D8 8 structure of Mn 5Ge 3 until one half of manganese is replaced; additional iron, then, may substitute in 6( g) sites. The postulated magnetic structure for Mn 5Ge 3 consists of ferromagnetic alignment of spins within the two sublattices and parallel alignment between them. When the Fe concentration exceeds 0.5, canting of spins occurs either between, or within, the sublattices. The limit of solubility of Fe in the structure appears to occur at, or slightly beyond, the Mn 4FeGe 3 composition.