The fluctuating temperature field in a jet stirred flow reactor designed fur chemical kinetic studies of hydrocarbon oxidation is investigated. In order to address both the question of the degree of micromixing and that of the turbulence/chemistry interaction, the present paper analyses and compares the fluctuating temperature structures inside this rc:actor for various situations. The experimental study is conducted by thr technique of fine-wire thermoanemometry. The pdfs, spectra and the relevant time scales of the temperature field are determined. In parallel, the fuel conversion rates of propane oxidation in all the experimental conditions are determined fi om a simulation work which takes into account a detailed kinetic model previously established. The variation of the unmixedness and the time scales of the temperature field is compared for a wide range of parameters in the reacting and non-reacting cases. The discussion is conducted in terms of the ratio between the time scales of the scalar and dynamic fields and of a Damkohler number.