n-heptane cracking has been carried out for very short time periods on an established reaction mechanism which includes the following group of stream reactions on different zeolites : Initiation reactions (protolytic cracking), charge isomerization, chain isomerization, hydride transfer, beta-scission-alkylation, desorption-adsorption, and hydrogen transfer-cyclization. It has been observed that a given experimental distribution of products can be explained by more than just one reaction scheme. This does not allow one to clearly distinguish the fraction of reactant which disappears via monomolecular initiation reactions with respect to bimolecular hydride transfer reactions.