The threshold for photoionization of C6F6 in solid neon was determined by irradiating a matrix sample in situ on scanning the energy of synchrotron radiation and by detecting the increased intensity of laser-induced fluorescence of the C6F6+ ion. A threshold energy of 10.08 +/- 0.02 eV was measured for photoionization of C6F6 in solid neon at 4 K. Relative to the ionization energy in the gaseous phase, this value corresponds to a barrier of 0.17 eV due to the matrix cage. The barrier is a result not only of interaction of the ejected electron with a noble gas host but also of other factors.