This paper deals with the strength characteristics of bolted joints subjected to torsional loads. The joints are composed of two hollow cylinders which are clamped by a bolt and a nut or a threaded tap bolt. The stress distributions at the contact surfaces and the variation in torsional loads occuring in the bolts are analyzed using an axisymmetrical theory of elasticity. A method for cstimating the joint strength for slipping is proposed. Analytical results concerning the variation of the torsional loads in the bolt and the joint strength are in fairly good agreement with the experimental ones. It is found that the joint strength for slipping increases as the initial clamping force increases. It is also found that the strength of joint using a bolt and a nut is greater than that using a threaded tap bolt. The joint strength when a torsional load is applied in the same direction as the screw fastening direction is greater than that in the inverse direction.