This paper reports on the solvent effect on energy transfer reactions in supercritical CO2. The energy transfer reactions are studied by steady-state and time-resolved fluorescence spectroscopy and the fluorophor/quencher reaction pairs are chosen to vary the reactions from diffusion-controlled to kinetically-controlled. In particular, the fluorescence quenching of anthracene by CBr4, 1,2-benzanthracene by CBr4, and anthracene by C2H5Br in supercritical CO2 at 35 degrees C has been reported. Experimental rate constants for the first two reaction pairs, anthracene/CBr4 and 1,2-benzanthracene/CBr4, follow the predicted diffusion control Limit at all pressures from 77.9 to 160.6 bar, indicating that local solvation does not enhance the reaction rate nor substantially impede the diffusion process in supercritical CO2. The rate constants for the third reaction, the quenching of anthracene by C2H5Br, are several orders of magnitude below the diffusion control limit, indicating that the reaction is kinetically controlled, as it is in liquids. Ln supercritical CO2 the apparent rate constants (i.e., those based on bulk concentrations of the reactants) for the anthracene/C2H5Br reaction decrease dramatically with increasing pressure. We believe that this apparently large pressure effect on the reaction rate is primarily due to the local composition enhancement of the quencher molecules around the dilute anthracene solute. This analysis is supported by fluorescence spectra and solvatochromic shift data of anthracene in pure CO2, and in mixtures of CO2 with C2H5Br at 35 degrees C that indicate both local density augmentation and local composition increases around the anthracene.