This paper presents the analysis of prismatic columns for their torsional behaviour. Such columns are widely used in the design of machine tools. The prismatic column is treated as a closed thin-walled beam and the problem is solved by using variational methods in conjunction with the finite difference technique. The results are compared with those obtained by using the cylindrical shell theory developed by Krishnamurthy . The effect of the thickness to breadth ratio and the length to breadth ratio on the torsional behaviour is studied. It is shown that the spacing and the number of diaphragms are important parameters when designing columns for torsional stiffeners. © 1974.