An attempt is made to clarify the characteristics of form effects on viscous resistance of ships. This paper is divided into two parts. The first half deals with the effect of transverse curvature on frictional resistance. As a continuation of the previous reports published some years ago, the turbulent flow over a circular cylinder moving in a direction of its axis is studied on the basis of the momentum integral method. Frictional resistance is calculated with consideration of the radius effect on velocity distributions. It has shown that the form effect influenced by the curvature is expressed as follows, K _{r 0}=1/4 L / r ₀ C _{f 0}, where L and r ₀ are the length and the radius of a cylinder respectively and C _{f 0} the frictional resistance coefficient of a flat plate. The latter half deals with the effects of londitudinal curvature of a two-dimensional body. The effects are separated into two parts, one due to friction and the other due to pressure. In this paper, the former is considered with the help of the Moriya's method for calculation of the potential velocity around a body. The following expression is derived for the form effect influenced by friction. K _{2 f} =2 (8/π C _w-1) B / L . Here C _w is the waterplane area coefficient and B the breadth.