Electronic structure calculations of the ordered ferromagnetic and paramagnetic transition metal alloys FeCo, Ni3Fe and Ni3Mn are performed using the full-potential linearized augmented plane wave method. The evolution of the electronic structure of alloys at disordering is studied in the framework of the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) combined with the local-density functional method. It is shown that the value of the magnetic moment is insensitive to order in all of the alloys investigated. The changes in the optical conductivity spectrum at the order-disorder transition are discussed. (C) 2002 Elsevier Science B.V. All rights reserved