The influence of annealing on the structure and some magnetic properties of Fe73.5Cu1Nb3-xUxSi13.5B9 (x = 1, 2, 3) alloys has been studied. The results confirmed the nanocrystalline character of these alloys in the temperature range 550-650 degrees C. The influence of the uranium content on the structural stability has been observed for annealing treatment at high temperature, i.e. at about 700 degrees C. The coercive field strongly depended both on the annealing temperature and on the uranium content. A minimum value of H-c was observed after annealing at 550 degrees C. Core losses of all alloys in the nanocrystalline state decreased with increasing uranium content.