The present paper investigate and illustrate the importance of plasma-particle interaction in controlling the plasma spray process while spraying alumina-titania powder blend. Plasma sprayed coatings of alumina-titania (60-40 mu m) have been prepared at different operating parameters. Phase composition of the coatings has been studied by X-ray diffraction technique. It is observed that chemical composition of alumina-titania coatings, prepared at low input power, is significantly different from that of the feed stock powder. Coating composition progressively approaches that of the feedstock powder at higher power inputs. Experimental results are explained in terms of the in-flight behaviour of alumina and titania particles in the plasma jet using a one-dimensional model to predict the thermal state of the particles. In particular, the effect of particle size and input power are considered in this study. (c) 2005 Published by Elsevier B.V.