Small scale experiments have been conducted of the spread of flames over the surface of thin filter paper sheets in a mixed convective flow moving in the direction of flame spread. The rate of flame spread has been measured as a function of the flow velocity and oxygen concentration. It is found that after an initial accelerating stage, the flame spread rate becomes constant as the flame progresses over the fuel surface. The initial acceleration period becomes shorter as the oxygen concentration is increased. The spread rate is weakly dependent on the flow velocity for low gas velocities (mixed flow) but becomes independent of the flow velocity for forced flow conditions. The flame spread rate is practically linearly dependent on the oxygen concentration of the flow over the range of concentrations tested. The data for the r a t e of flame spread can be correlated in terms of an expression of the spread rate that is obtained from a simplified heat transfer model of the flame spread process.