A theory is developed for particulate deposition rate on surfaces from turbulent gas streams. The three characteristic times, the particle equilibration time, the turbulent fluctuation time, and the particle residence time, control the deposition mode. The larger particles reach the wall across the laminar sublayer because of the momentum imparted to them by the turbulence velocity of the fluid. The smaller particles, on the other hand, diffuse to the wall by thermophoresis which depends on the temperature gradient. The computed results of the theory for pipe flow are compared with the available experimental data and satisfactory agreement is shown.