Shock waves are reflected from a wall in the presence of a transverse magnetic field. The gas is highly ionized and therefore the lines of force can be considered ``frozen in.'' In such a case the magnetic field is compressed and the Rankine‐Hugoniot relations, including magnetic pressure and magnetic energy as given by de Hoffmann and Teller, are used. The magnetic probes show an increase of the magnetic field behind the reflected shock, and the velocity of the reflected shock waves (measured from streak camera photographs) increases with increasing fields. For a constant incident velocity, the dependence of the reflected shock velocity on the magnetic field is given by a linear function:Ur2=a+bB2whereaandbare constant in a first approximation. This law has been verified by experimental results.