The aerodynamic forces on golf balls were studied by dropping spinning balls through the horizontal wind stream of the B. F. Goodrich wind tunnel. The lift,L, and drag,D, were calculated from the drift of the balls, rotating at speeds,N, up to 8000 r.p.m. while falling through a wind stream having a velocity of 105 feet per second. For a standard dimple or mesh golf ball weighing 0.1 lb., the lift varied with the rotational speed asL=0.064 ×[1−exp(−0.00026N)], with a maximum observed value of 0.055 lb. or more than half the weight of the ball. The drag increased nearly linearly from about 0.06 lb. for no spin to about 0.1 lb. at 8000 r.p.m.For a smooth ball the lift was negative at all rotational speeds below 5000 r.p.m. Above this speed, the lift was positive but was less than for the standard ball. The drag for these balls was nearly constant at about 0.08 lb. Balls with shallower dimples than standard gave intermediate results. Driving tests were consistent with the wind tunnel results.These results explain why a golfer cannot obtain long drives with a ball having a smooth surface and why the standard dimple or mesh surface gives him greater distance and better control of the ball.