Solutions of ethylene in cyclohexane have been irradiated with cobalt-60 gamma rays. Some experiments were carried out in the presence of oxygen, carbon tetrachloride or ammonia. The results indicate that ethylene reacts with hydrogen atoms to form radicals, which are precursors to ethane and ethylcyclohexane formation. These products are also formed by reactions between cyclohexane positive ions and ethylene. The contribution of these ion-molecule reactions can be enhanced by addition of electron scavengers such as carbon tetrachloride and is reduced in the presence of ammonia. It is concluded that thermal hydrogen atoms are formed in irradiated cyclohexane with a yield which is equal to or smaller than 0.8.