An experimental investigation is carried out on a flow around a circular cylinder vertically mounted on a smooth plane wall along which a turbulent boundary layer is fully developed. Pressure drag of the cylinder is correlated with the height h, the diameter d of the cylinder and the characteristics of the boundary layer. The pressure drag coefficient C_D is found to be expressed in the form C_D=a(h/δ)^b, where δ is the thickness of the boundary layer and the values of a and b are dependent on h/δ. when h/δ&lsin; 1. 1, a and b are linear functions of d/δ, while they are constant in the range h/δ> 1. 1.