Ni80Nb20, Ni60Nb40, Ni40Nb60, Ni60Nb20Zr20 and Ni60Zr40 amorphous alloys were prepared by mechanical alloying. The structure and thermal behaviour of the amorphous alloys were studied by X-ray diffractometry and differential scanning calorimetry and were compared to corresponding melt spun materials. In Ni-Nb amorphous alloys the mean nearest-neighbour distance and the thermal stability both increase with increasing Nb content. Substitution of Nb by Zr in Ni60Nb40 amorphous alloy also increases the mean nearest-neighbour distance, but reduces the thermal stability.