The resistance to rolling is of great importance to investigate the safety of vessels in rough seas. The passive resistance due to the action of the water is mainly composed of three kinds, i.e. , the frictional resistance, the eddy making resistance and the wave making resistance Of these resistances only the wave making one was shown in the author's previous paper to follow the law of comparison for similar ships. It is therefore necessary to establish formulae for the frictional and eddy making resistances in order to extend the results of model experiments to actual ships. In the present paper new formulae for the frictional resistance are obtained after analysing the results of experiments on the oscillations of suspended cylinders wholly immersed in the water. The frictional coefficient C_f for oscillating cylinders is found to be expressed in the form exactly same as that given by H. Blasius for laminar flow, if Reynolds number R_n be taken as 3.22 r ²θm²/T_v The decrement of roll per swing due to friction for a ship model without bilge keels in fresh water is given by the formula d θ_f=2.11 Sr _s ²θ _m / WmT ^1.5 at 15°C in kg, m, sec, deg, units : and the decrement for a ship model with bilge keels is written as d θ_f=2.11 Sr _s²θ _m / WmT ^1.5 {1+0.143 ( r _s θ _m ) ^0.772/ T ^0.386} at 15°C.in which the frictional coefficient for turbulent flow is used from the following formula given by G. Hughes C_f= 1.328R_n^-0.5 + 0.014R_n^-0.114. The value of δθ_f for a ship in salt water is shown as d θ_f=2.22 Sr _s²θ _m / WmT ^1.5 {1+0.141 ( r _s θ _m ) ^0.772/ T ^0.386} at 15°C. Though the mean radius rs for the wetted surface may be calculated by using the formula r _s=√1/S∫∫ r ²sin²α dldx , it is easily and in close approximation obtained from the following formula r _s=1/π {(0. 877+ 0.145 C_b ) (1.7 d+ C_b · B ) -2×OG}, where C_b is the block coefficient, d the mean draught, B the breadth of ship and OG the value of ( d - KG ). The ratio of δθ_f to the total decrement δθ at the mean angle of roll of 5 degrees for ordinary ship models 2 m in length is ranging from about 7 to 16 per cent, while the ratio at the mean angle of roll of 20 degrees is from 3 to 7 per cent. This ratio for actual ships is found to be between one tenth and one fifth of that of ship models.