Vapour-liquid, liquid-liquid and liquid-liquid-vapour equilibria for the system 1,1,1,2-tetrafluoroethane + heptylbenzene were determined in the temperature range from 260 to 400 K and at pressures up to 12 MPa. The system was found to be a type 11 system according to the classification of Van Konynenburg and Scott. The (l(2) = l(1))9 critical endpoint was found at T = 320.07 K and P = 1.155 MPa. The mole fraction of heptylbenzene in the critical liquid phase in the critical endpoint is approximately 0.20. (C) 2003 Elsevier Science B.V. All rights reserved.