flow mixing calorimeter followed by a vibrating-tube densimeter has been used to measure excess molar enthalpies H-m(E) and excess molar volumes V-m(E) of {xC(4)H(10) + (1 - x)SF6}. Measurements over a range of mole fractions x have been made in the supercritical region at the pressure p = 6.00 MPa and at seven temperatures in the range T = 311.25 K to T = 425.55 K. The H-m(E)(x) measurements at T = 351.35 K were found to exhibit an unusual double maximum. Measurements at all temperatures are compared with the Patel-Teja equation of state with the parameters determined by solving a cubic equation as recommended, and also with parameters determined by the method suggested by Valderamma and Cisternas who proposed equations which are a function of the critical compression factor. The overall fit to the H-m(E) and V-m(E) measurements obtained using Valderamma and Cisternas equations was found to be better than that obtained using the parameters according to the method suggested by Patel and Teja. (C) 2003 Published by Elsevier Science Ltd.