In this work experimental vapour-liquid and solid-fluid equilibrium data are presented for 13 different compositions of the system methane + triacontane. This data cover the temperature range from 315 to 450 K, and pressures up to 200 MPa. The compositions studied range from almost pure methane to pure triacontane. On the basis of the primary experimental two-phase equilibrium results, the course of the three-phase curve (solid triacontane + liquid + vapour) was derived. The second critical endpoint of this curve, where solid triacontane is in equilibrium with a critical fluid phase (s(C30) + (l = g)) was found at T = 340.73 +/- 0.4 K, P = 128.55 +/- 0.5 MPa and a mole fraction in the critical fluid phase of x(C30) = 0.0275 +/- 0.002. (C) 2004 Elsevier B.V. All rights reserved.