A two-colour pyrometer was developed for the measurement of the surface temperature of particles in flight in a DC plasma-spraying jet which is characterised by high temperatures (up to 10000 K), high velocities (more than 500 ms^-1) and very steep radial temperature gradients (3000 K mm^-1) and velocity gradients (300 m s^-1 mm^-1). Measurements of surface temperature have been made on metallic (Ni) or ceramic powders (ZrO₂, Al₂O₃) with mean diameter of 10-100 mu m. The surface temperatures of the particles range from 2000-4000 K and their velocities (measured simultaneously by laser anemometry) are from 50-300 m s^-1. One of the major difficulties of pyrometry in such flows is the plasma radiation, especially in the jet core.