Data are presented on the short and long term energy stability of the 22‐Mev betatron at the University of Illinois. The data were taken in the course of a detailed study of the O16(&ggr;,n)O15yield curve. It is concluded that the machine was often stable to better than ±3 kev for periods of several hours, and that the maximum energy fluctuation which was observed over an eighteen month period was 40 kev at 17 Mev.