A study is made of the suitability of 1,1,1-trichlorotrifluoroethane for use as matrix in spectroscopic studies of radiation-produced radical cations. After irradiation of the pure compound with cobalt-60 gamma rays at 77 K a complex absorption is observed, consisting of a band at 600 nm and a composite band around 360 nm. Addition of alkanes before irradiation results in the appearance of an important new absorption band, which may be assigned to the corresponding alkane radical cations. The long wavelength component and much of the short wavelength component of the matrix absorption may easily be photobleached, without seriously affecting absorption bands of trapped alkane radical cations studied. These absorption bands may selectively be eliminated by a second bleaching and pure spectra obtained by difference spectroscopy. Some of the complexities arising from working at high erabsorbed doses (7.5 1019eV.g−1instead of 7.5 1018eV.g−1) are being discussed.