This paper presents a simplified method for the design and analysis of non-prestressed, partially prestressed, and fully prestressed concrete beams subjected to pure torsion. The proposed model relates the torsional strength to the concrete compressive strength and to the amounts of transverse and longitudinal reinforcement. To check the adequacy of this simple method, the calculated strength and mode of failure are checked against the experimental results of 17 prestressed concrete 66 reinforced concrete beam tests available in the literature, and very good agreement is found. The simplicity of the method is illustrated by two examples, one for design and another for analysis.