Lysophosphatidylcholine (LPC) is a bioactive proinflammatory lipid generated by pathological activities. LPC is also a major phospholipid component of oxidized low-density lipoprotein (Ox-LDL) and is implicated as a critical factor in the atherogenic activity of Ox-LDL. LPC is believed to play an important role in atherosclerosis and inflammatory diseases by altering various functions in a number of cell-types, including endothelial cells, smooth muscle cells, monocytes, macrophages, and T-cells. LPC activates several second messengers -- including protein kinase C, extracellular-signal-regulated kinases, protein tyrosine kinases, and Ca(2+) -- implicating the engagement of transduction mechanisms in its observed actions. Moreover, recent evidence suggests that in several cell-types, cloned orphan G-protein-coupled receptors may serve as the specific receptors via which LPC modulates second messenger pathways (although LPC may not be a direct ligand of such receptors). In addition, current evidence suggests that LPC impairs the endothelium-dependent relaxations mediated by endothelium-derived relaxing factors and directly modulates contractile responses in vascular smooth muscle. However, despite all this, and although elevated levels of LPC have been linked to the cardiovascular complications associated with atherosclerosis, ischemia, and diabetes, the precise pathophysiological roles played by LPC in several states remain to be established. In this review, we focus in some detail on the entirety of the signal-transduction system for LPC, its pathophysiological implications, and the vascular abnormalities associated with it.