The influence of chain length on cracking reactions of linear paraffins on acid catalysts has been examined. Whether studied as individual reactants, as components of simple mixtures of paraffins, or as minor constituents of complex industrial FCCU feedstocks, increasing chain length of n-paraffins is associated with increasing cracking reactivity. This increase in reactivity cannot be accounted for solely by considering the increase in the number of carbon atoms or the number of crackable bonds in the molecular structure. However, by simultaneously taking into account adsorption phenomena and crackable bonds, good correlations between observed rates and predicted behavior are obtained, both for cracking of individual paraffins and for components of simple paraffin mixtures. Reasonable correlations are also observed for cracking rates of linear paraffins as components of industrial FCCU feedstocks. The presence of other components in the feed can influence the crackability of linear paraffins but does not have a major influence on the relative cracking rates of linear paraffins due to chain-length effects.