Muon spin rotation spectra of muoniated radicals of the enediyne compounds (E)- and (Z)-RCequivalent toCCH=CHCequivalent toCR where R = -CH2CH2CH2CH3 are reported and the temperature variation of these spectra from 250 to 400 K investigated. All primary radicals expected were observed and assigned using ab initio DFT calculations. The properties of a six membered secondary radical likely to be formed by the cyclization of the muoniated Z-isomer were estimated using an ab initio DFT calculation.