The characteristic features of interstellar gas clouds—existence of large density fluctuations, their connection with cosmic dust, stretching along the magnetic fields, and so on—may be described by a shock wave theory in interstellar space.The author has developed a theory of stationary shock waves accompanied by losses of energy by means of radiation. Choosing two surfaces on both sides of the front, so that the regions of energy radiation should lie between them, we can write an equation for the mass flow and for the impulse conservation between these surfaces, and two equations which determine the stationary temperature of the gas in the field of interstellar radiation. The solution of this system of equations permits one to determine the general changes of thermodynamic and other parameters for the transition of gas through the shock wave with regions of radiative cooling. If changes of the degree of ionization take place, and a magnetic field is present, some terms should necessarily be added to the corresponding equations.The boundary between the interstellar gas cloud and the intercloud medium must represent the shock wave accompanied by losses of energy by means of radiation, because such ruptures may probably be supposed as the sole explanation of stability of the great density changes (a hundred times and more) often observed in the interstellar space.In this paper we give some results of the theory of shock waves accompanied by radiative losses of energy.