The phase behaviour of the saturated monoacid triglycerides tripalmitin, tristearin and triarachidin has been studied for the pure compounds at normal pressure as well as under the influence of dissolved helium, nitrogen and argon at pressures up to 20 MPa with thermal analysis according to Smit. Under the experimental conditions applied two phase transitions are observed during the linear heating process for all triglycerides and all gases : transition from the metastable alpha-phase into the thermodynamically stable beta-modification and the melting of the beta-modification. Within the pressure and temperature range which has been examined the T(p) phase boundaries form essentially straight lines with slopes depending on the dissolved gas. Generally the slopes decrease when changing from helium to nitrogen and from nitrogen to argon. From the difference between the transition temperatures under helium and nitrogen as well as under helium and argon at a given pressure the mole fractions of dissolved nitrogen and argon are estimated as a function of pressure.