An experimental investigation of the behaviour of reinforced concrete column!; and a theoretical procedure for analysis of both short and slender reinforced and composite columns of arbitrarily shaped cross section subjected to biaxial bending and axial load are presented. In the proposed procedure, nonlinear stress-strain relations are assumed for concrete, reinforcing steel and structural steel materials. The compression zone of the concrete section and the entire section of the structural steel are divided into adequate number of segments in order to use various stress-strain models for the analysis. The slenderness effect of the member is taken into account by using the Moment Magnification Method. The proposed procedure was compared with test results of 12 square and three L-shaped reinforced concrete columns subjected to short-term axial load and biaxial bending, and also some experimental results available in the literature for composite columns compared with the theoretical results obtained by the proposed procedure and a good degree of accuracy was obtained. (C) 2007 Elsevier Ltd. All rights reserved.