This study deals with the effect of temperature on the gas-chromatographic behaviour of thiols, alkanes, branched-chain alkanes and cyclic alkanes on polyester (LAC-446, LAC-745, LAC-772, LAC-860, LAC-886, LAC-841 and LAC-935) liquid stationary phases. Increases were observed in specific retention volumes as well as improvements in the separations at certain temperatures. The critical temperatures were different for the various liquid stationary phases; these were 110 째C for LAC-446 and LAC-886 and 120 째C for LAC-860 and LAC-772. Differential-thermal analysis of two of the liquid stationary phases indicated a change in the physical properties of the polymers during heating.