Heat transfer in the combustion chamber of s.i. engines operating under knocking conditions has been detected and analyzed. Measurements have been carried out, cycle by cycle, on a CFR laboratory engine by means of a dedicated instrument and an original method. The relationship between heat transfer and knock intensity has been analyzed on a statistical basis, emphasizing knock intensity influence on heat transfer distribution. Moreover, the share of heat transfer more closely related to knock intensity has been highlighted: heat transfer is shown not to be significantly affected by knock intensity under light-to-medium knock conditions; on the contrary, the influence becomes evident under medium-to-heavy knock conditions.Eventually, heat transfer indexes influenced by knock intensity have been evaluated, allowing a comparison of knock-related thermal properties of fuels.