Fe-Pt alloy films were electrodeposited in a novel bath containing ammonia solution and ammonium tartrate as complexing agent. The compositions of the Fe-Pt deposited films were controlled by bath composition and current density. The crystallographic structures of deposited films with compositions ranging from 34.0 at.% Pt to 81.8 at.% Pt were analysed by means of XRD, HRTEM and ESCA. The crystallographic structure of all the deposited films, which were obtained in the present study, consisted of a single solid solution of a face-centred cubic structure.