A Fe-20Mo-5Ni-0.075C (wt %) alloy for magnets was prepared by induction melting under vacuum. The material was hot rolled, solution treated and aged at 610 degrees C for different periods of time. The magnetic properties (H-c, B-r, B-s and (BH)(max)) were measured and compared with some commercial alloys containing cobalt. The precipitation of Mo-rich phases and the decrease of the ferrite lattice parameter during ageing were detected by X-ray diffraction. The thermomagnetic analysis (TMA) was carried out in the solution treated samples and aged samples. The behaviour of TMA curves was explained with the help of X-ray analysis.