(Mn(0.54)AI(0.46))(100-x)La-x and (Mn(0.535)AI(0.448)C(0.017))(100-x)La-x alloys, with x up to 0.9, were synthesized and examined by powder X-ray diffraction and magnetic measurements. Lattice parameters, Curie temperature, T-C, coercivity, iH(C), and saturation magnetization, M(S), were determined. Phase analysis revealed that AI(8)LaMn(4) precipitates were produced due to the lanthanum addition. A slight increase in the iH(C) was observed for x less than or equal to 0.3 in the cast MnAILa alloys. No significant changes in lattice parameters and T-C were observed for these lanthanum-doped alloys. For sintered isotropic magnets, which were prepared by conventional powder metallurgy processes, the iH(C) was enhanced on doping with lanthanum. The (BH)max values were also increased. The increment of (BH)(max) was about 16% for x=0.3. Higher lanthanum intensity at grain boundaries was observed on examination of the energy-dispersive X-ray spectra (EDX). The reasons for the increase in iH(C) may be due to the fine precipitates of lanthanum in the grain boundaries.