In the paper, a numerical procedure for investigation of slender reinforced concrete columns and steel-concrete composite columns at normal and high temperatures is presented. The procedure is based on sectional analysis and moment-curvature approach. Its applicability is illustrated on validation examples in which the results obtained by the simulations are compared with the test data given in literature. It is shown that the procedure provides sufficiently accurate results. The procedure was implemented in an in-house MATLAB code. The code is employed for the calculation of the examples presented in the paper. The code was also included in freely available scientific computer programs. The procedure is applicable for normal and high temperature conditions and for columns of symmetrical cross-sections of any type and shape. It is applicable in connection with any type of temperature-time curve, heat transfer model, and material models.