Schilieren spark snapshots spaced at electronically controlled intervals of several hundredths of a millisecond show the emergence of the shock wave and the formation of the vortex ring at the end of a cylindrical shock tube, open to the atmosphere. The axial positions of the vortex ring and shock front are plotted as a function of time for the first millisecond, in which time the vortex forms and is accelerated to about three‐quarters of the theoretical particle velocity of the mass flow following the initial plane shock. The diameter of the vortex ring increases nonlinearly with time and distance.