The effect of ether lipid 1-O-Octadecyl-2-O-methoxy-rac-glycero-3-phosphocholine (ET-18-OCH3), platelet activating factor (PAF) and carbamyl activating factor (CPAF) on the release of IL-6 in human thymic epithelium cultivated in vitro was studied. ET-18-OCH3 significantly increased the release of IL-6, giving the greatest effect at the dose of 2 micrograms/ml. PAF had no effect. The non-metabolizable CPAF was less effective than ET-18-OCH3 and showed the greatest release of IL-6 at the dose of 1 microgram/ml. Ether lipid ET-18-OCH3 has a thymotrophic effect as has also been demonstrated by other results obtained in our previous work.