Experiments have been performed to investigate the film cooling characteristics of steam injection through three staggered rows of 60 degree inclined holes over a straight aluminum airfoil with a circular leading edge. The axial distance between cooling hole rows is five hole diameters. The lateral distance is four hole diameters. Data have been taken for the local film cooling effectiveness of steam and air with blowing rates varying from 0.3 to 1.8. It shows that at small blowing rates, steam has an effectiveness up to 2.5 times greater than air; but, as the blowing rates are increased, the difference between the steam and air effectiveness is gradually decreased. It also shows that the steam effectiveness is less dependent upon the blowing rates than is the air effectiveness. The results generally support the previous analytical prediction.