In this paper, we examine the soot yield from a propane diffusion flame in a cross-flowing air stream. Soot yield, defined as the net amount of soot per gram of fuel, from a diffusion Hame in cross-flow was compared to that from a diffusion flame in co-flowing air. We observed that the orientation of the fuel jet relative to the air stream has a significant effect on the flame shape and on the soot yield. We varied the air velocity, fuel velocity, and jet diameter to determine The effect of each of these on the soot yield from the flame in cross-flow. At low air velocities, increasing the air velocity decreases the soot yield dramatically but further increases do not have a significant effect unless the fuel velocity is increased also. The jet diameter does not affect the soot yield at a constant velocity. Finally, we propose a correlation of our data to a "mixing index" defined as the product of the air and fuel velocities.