Photochemically generated benzyl radicals react with C₆₀ producing radical and nonradical adducts R_nC₆₀ (R = C₆H₅CH₂) with n = 1 to at least 15. The radical adducts with n = 3 and 5 are stable above 50°C and have been identified by electron spin resonance (ESR) spectroscopy as the allylic R₃C₆₀^. (3) and cyclopentadienyl R₅C₆₀^. (5) radicals. The unpaired electrons are highly localized on the C₆₀ surface. The extraordinary stability of these radicals can be attributed to the steric protection of the surface radical sites by the surrounding benzyl substituents. Photochemically generated methyl radicals also add readily to C₆₀. Mass spectrometric analyses show the formation of (CH₃)_nC₆₀ with n = 1 to at least 34.