In this paper, the phase behavior of a naturally occurring reservoir fluid mixture has been experimentally studied in the near-critical region. The computer-controlled ROP (France) high-pressure PVT system equipped with video camera-monitor-recorder system and an on-line Anton-Paar fluid density meter was used in the experimental work. The measurements involve the compressibility factor of the compressed fluid, the bubble/dew point locus in the near-critical region, the mixture critical point, the liquid volume fraction in the two-phase region, and the density of the liquid/vapor phase. The volume-translated Soave-Redlich-Kwong equation of state proposed by Peneloux and Rauzy (1982) [Peneloux, A. and Rauzy, E., 1982. A consistent correction for Redlich-Kwong-Soave volumes, Fluid Phase Equilibria, 8 : 7-23] was selected to test its performance in the near-critical region. The C-7(+)-fraction of the reservoir fluid was characterized by the procedure proposed by Pedersen et al. (1984) [Pedersen, K.S., Thomassen, P. and Fredenslund, Aa., 1984. Thermodynamics of petroleum mixtures containing heavy hydrocarbons. 1. Phase envelope calculations using Soave-Redlich-Kwong equation of state. Ind. Eng. Chem., Process. Des. Dev., 23 : 163-170].