Summary: Two formulations of the Monte Carlo method based on the reciprocity principle, considered from both points of view of the reverse path and the exchanged power, are developed and discussed. Their results are compared to those of a conventional forward Monte Carlo approach in 1D benchmark cases involving gray media or actual gas-mixtures and different optical thicknesses and thermal conditions. Gas radiative properties are treated in a correlated manner by a CK model. Although these problems are 1D, the calculations have been carried out with 3D calculation grids in order to check the capacity of the different approaches for dealing with actual 3D systems. Advantages and drawbacks of the three formulations are discussed. In terms of computation time, it is not more expensive to obtain the results from the three approaches (with only one calculation) than to obtain the results from one given approach.