We have studied three kinds of amorphous Ni-Zr alloy thin films, prepared by solid state reaction in layered nickel and zirconium films and by dual electron gun codeposition. The codeposited films have a homogeneous composition of Ni1Zr1 and Ni1Zr2. The reacted alloys have a composition gradient ranging roughly from Ni50Zr50 to Ni64Zr36. The alloys have been characterized by differential scanning calorimetry, in situ resistivity measurement, transmission electron microscopy and Rutherford backscattering spectra. A comparison has been made of the three kinds of amorphous alloys in terms of their stabilities, crystallization behavior and diffusion characteristics.