Oxygen, which is the subject of this symposium is probably created during the helium-burning phase of stars. The nuclear reactions involved in the production of the three stable isotopes of oxygen are shown in Fig. 1. The stepwise reactions in which O16, O17 and finally O18 are produced probably occur at temperatures of the order of 108 degrees Kelvin and at very great pressures (i.e. densities of 105 gm per cm) [1].