The influence of ethene and propene on the catalytic cracking of n-heptane at 673 K over the USHY zeolite has been studied with mixtures of n-heptane with different concentrations of alkene. The study reveals that the presence of light alkenes, with an alkene-to-n-heptane molar ratio in the range of 0.1-1.2, results in a decrease of the initial cracking activity of n-heptane, and an increase in the yield of heptenes and amount of coke formed. So, for this range of relatively high concentrations of light alkenes studied, die cracking reaction of n-heptane is substantially inhibited by these species.