Protection of a substance against certain modes of radiolysis by introduction of a low-concentration solute which can interfere with the normal fate of some primary intermediate can be achieved by a variety of mechanisms (1). The system most extensively studied in this connection is cyclohexane + benzene. Reduction of the yield of hydrogen and ethylene by addition of small amounts of benzene to cyclohexane is not adequately explained solely on the basis of a scavenging process in which benzene intercepts H atoms (2, 3). An alternative suggested mechanism of such observed protection is energy transfer (via either charge or virtual photon) from cyclohexane to the more stable benzene. This paper describes and interprets results of additional studies of the effects of iodine and other additives on the yield of hydrogen from the cyclohexane + benzene system. Similar experiments by Schuler (4) have recently been reported.