The paper presents the internal energy budget in the initial region of the slightly heated free round jet in the presence of column-mode coherent structures. The budget was obtained by the quantitative evaluation of the shares of particular streams of internal energy transported in the flow-field considered. The input data for calculations have been obtained by the hot-wire measurements of three components of instantaneous velocity and instantaneous temperature. All the terms of the internal energy budget have been determined experimentally except the pressure-velocity term which was treated as a closing quantity. The results of the study suggest, that the internal energy of the flow is determined by the mutual balance of convection realized by the mean, oscillatory and random components of motion accompanied by the work of pressure-velocity correlations. It appears furthermore, that the heat transfer in the initial jet area is realized mainly by random fluctuations of proper turbulence motion, generated, however, in substantial part by coherent structures existing in the flow-field considered. (C) 1997 Elsevier Science Ltd.