Experimental results of the high pressure phase behaviour for {x(1)CF(4) + x(2)NaCl + (1-x(1)-x(2))H2O} are presented. (Gas + gas) equilibria for 10 compositions, with mole fractions of CF4 (0.0076 +/- 0.0002) < x(1) < (0.0335 +/- 0.0002), and NaCl (0.0032 +/- 0.0002) < x(2) < (0.0103 +/- 0.0002) were measured in a high-pressure autoclave with sapphire windows and magnetic stirring. Phase transitions were determined visually. The pressure range was from 20 MPa to 200 MPa and the temperature range from T = 585 K to T = 663 K. Isopleths for NaCl mass fractions omega = (0.011, 0.021 and 0.033) relative to H2O are shifted towards higher temperatures compared with the binary mixture {xCF(4) + (1-x)H2O}. The objective of this study was the investigation of the phase behaviour of a model-system encountered in supercritical water oxidation processes.