The room temperature, liquid phase radiolysis of cyclohexane in the presence of three solutes, per fluorocyclohexane (PCH), perfluoromethylcyclohexane (PMCH), and perfluorocyclobutane (PCB) has been examined. All decrease the hydrogen yield from 5.6 to 2.6 G units by capturing electrons. However, with PMCH and PCB the yields of cyclohexene and bicyclohexyl are not decreased as much as the hydrogen yield and with PCH, dimer and olefin yields are increased. Furthermore, large yields of monohydrofluorocarbon (e.g. undecafluorocyclohexane) are produced, indicating that a carbon–fluorine bond has been broken. It is concluded that electron capture by these fluorocarbon compounds causes dissociation; possible mechanisms are discussed, but it was not possible to reach a clear conclusion on the basis of our results.The radiolysis of homogeneous solid solutions of these solutes at 77 °K has also been studied, but only PMCH was studied in detail. Under these conditions there is no evidence for dissociative electron capture and apparently the combination of solute anion and hydrocarbon cation on warming does not lead to bond breaking.