(Ti, Al) alloy nitride films have drawn much attention because of their excellent oxidation resistance. The purpose of this paper is to investigate the structure, morphology and composition of the (TiXAl1-XNY films prepared by r.f. reactive sputtering using a composite target where the area ratio of Ti to Al is unity. Nitrogen flow to total nitrogen and argon flow ratio (F-N2/F-total) is used as a parameter. The partial pressures of these gases that resulted were monitored by their optical emission in the glow discharge. The crystallographic structure of deposited films were divided into three groups by the F-N2/F-total that was used in their preparation. The first group (F-N2/F-total=0) is a Ti and Al metal mixed structure. The second group (0.1 less than or equal to F-N2/F-total < 0.4) has an amorphous structure. The last group (F-N2/F-total greater than or equal to 0.4) has the wurtzite structure. Under all conditions, the composition of the films was richer in Al than the target area ratio of Ti to Al, as would be expected from their sputtering yields. This ratio changes with admission of nitrogen because of selective poisoning (the formation of nitrides on the sputtering target). The plot of composition ratio C-Ti/C-Al vs. F-N2/F-total showed the local minimum at about F-N2/F-total = 0.3. The ratio of Ti to Al emission intensity, I-Ti/I-Al, from optical measurements shows excellent agreement with C-Ti/C-Al. It is concluded that the optical emission signal is very useful for the composition control during deposition, both of the materials being sputtered and of the residual atmosphere.