Experimental densities for n-perfluorohexane and n-perfluorononane were measured using a vibrating tube densimeter at pressures ranging from 0.1 to 40 MPa, and at temperatures varying from 283.15 to 313.15 K for the former, and from 283.15 to 343.15 K for the latter. Thermomechanical coefficients as the isobaric thermal expansion, isothermal compressibility, and internal pressure were calculated from these density data. This set of experimental compressed liquid densities was used for a comparative study of the performance of several EOS. Best results were obtained with a volume translated Sako-Wu-Prausnitz equation. (C) 2004 Elsevier B.V. All rights reserved.