Ultrafine nanosized powders of TiO2 and TiN have been synthesized by the reactive ion-beam evaporation technique. In an oxygen or nitrogen atmosphere (1-10 Torr), a high-power-density ion beam (about 0.4 GWcm(-2)) is focused onto a Ti target; as a result of the interaction between ablated particles and gas, fine and ultrafine powders are synthesized. The influence of gas pressure and target-collector distance on the particle composition, size distribution and shape have been studied. At longer target-collector distances and higher pressures, powders in the 4-45 nm range are collected while, at shorter distances and lower pressures, the powders are in the micrometre range. TiO2 particles are spherical in shape, while TiN particles are cubic.