The vapour phase synthesis of anisole by O-alkylation of phenol with methanol was investigated over lanthanum, cerium, samarium, and antimony phosphate catalysts promoted with cesium hydroxide. Among various catalysts investigated, the cesium promoted samarium phosphate provided better activity and selectivity. The effect of temperature, contact time, time-on-stream, reusability, and up-scaling of the catalyst were also studied. These studies clearly reveal that the Cs-Sm combination is the superior catalyst for selective O-alkylation of phenol with methanol. The unpromoted catalysts provided more C-alkylated side products. Incorporation of cesium suppressed the formation of side products. The X-ray diffraction analysis of various samples revealed that there is no change in the crystalline composition of the catalysts up on addition of cesium promoter. However, the surface acidity of the catalyst was observed to decrease after the incorporation of cesium promoter as revealed by the temperature programmed desorption study of anhydrous ammonia. (C) 2002 Elsevier Science B.V All rights reserved.