The results of first-principles virtual-crystal calculations for the GaxAlyIn1-x-yN disordered alloys are presented. Electronic structures and energy gaps of the alloy with zinc blende and wurtzite structures have been studied as a function of composition (x,y) for the whole range (x,y=0 to 1). The energy gap of the alloy Eg(x,y) with a wurtzite structure has been found.