Magnetic properties (saturation magnetizations, anisotropy fields and Curie temperatures) of alloys of the composition Nd
2Fe
12-xMn
xCo
2B with

are presented. All of the alloys studied crystallize in the tetragonal Nd
2Fe
14B structure. With substitution of Fe by Mn, the Curie temperatures and saturation moments decrease. The anisotropy field, H
A, is found to increase. Theoretical energy products are reduced from 65 to 58 MGOe when Fe is replaced by Mn to the extent of x =1.