In the conversion of C-13-labelled pentanes in the presence of aluminium halides and superacids, the distribution of the label in the isomerization products fails to comply with any of the existing schemes of this reaction within the framework of classic ionic mechanisms. Furthermore, when the process was carried out in a deuterium atmosphere, by mass-spectral analysis it was established that molecular hydrogen is not included in the general scheme of the isomerization process. An alternative mechanism of catalytic isomerization of alkanes in the presence of acids is examined, assuming that the activation of a substrate molecule occurs not as a result of detachment of a hydride ion, but by its single-electron oxidation with the formation of cation-radicals as primary intermediates.