Lysophosphatidylcholine (LPC), 1-acyl-sn-glycero-3-phosphocholine, is well known as an intermediate of metabolism of phosphatidylcholine (PC), the main phospholipid component in all eukaryotic and many prokaryotic cells. LPC is produced as a result of PC hydrolysis by several isoforms of phospholipase A2 (PLA2) and in the reaction mediated by lecithin-cholesterol acyltransferase that transfers the fatty acid residue from PC to cholesterol. LPC is classified as a second messengers that is produced by activation of cytosolic hormone-activated PLA2. It was shown that LPC inhibits transmembrane signaling via receptors, which in their active form are linked to G-proteins. There is a viewpoint that LPC abolishes formation of the complex between the receptor and G-protein. The effect of LPC on protein kinase C (PKC) activation is considered in this review. It was shown that low (less than 20 microM) and high (more than 30 microM) concentrations of LPC activated and inhibited PKC, respectively. The mechanism of LPC-induced activation of PKC still remains unclear. However, the studies of the effect of LPC on signal transduction through the PKC-mediated pathway showed that LPC probably plays an auxiliary role. It was suggested that LPC may prolong the effect of the direct activators of PKC (such as 1,2-diacylglycerol or phorbol esters). The physiological role of the elevation of LPC level in tissues is associated with its ability to enhance or even evoke cell proliferation, stimulate adhesion and differentiation of lymphoid cells, have mitogenic effect on macrophages, activate human T-lymphocytes, initiate monocyte chemotaxis, decrease myocardial sensitivity to cholinergic stimulation, impair contractility of arterial smooth muscle, and modulate aggregation of platelets.