The effects of the glassy and polycrystalline states of methylcyclohexane (MCH), isopentane (IP), isohexane (IH) and 2,3-dimethylbutane (DMB) on the yields of the heavy products from the γ-radiolysis has been investigated. Total G values are the same in glassy and polycrystalline solids for MCH and IP, but G values for IH and DMB are larger in the polycrystalline states than those in the glassy forms. Comparison of the relative distribution of stable products always shows matrix effects. Differences in esr spectra between either states have only been observed for irradiated IH and DMB. The results from radical scavenging methods are interpreted in terms of different probabilities of radical processes in the glassy and polycrystalline states.