The antitumor ether lipid ET-18-OCH3 (edelfosine) is the prototype of a new class of antineoplastic agents, synthetic analogues of lysophosphatidylcholine, that shows a high metabolic stability, does not interact with DNA and shows a selective apoptotic response in tumor cells, sparing normal cells. Unlike currently used antitumor drugs, ET-18- OCH3 does not act directly on the formation and function of the replication machinery, and thereby its effects are independent of the proliferative state of target cells. Because of its capacity to modulate cellular regulatory and signaling events, including those failing in cancer cells, like defective apoptosis, ET-18-OCH3, beyond its putative clinical importance, is an interesting model compound for the development of more selective drugs for cancer therapy. Although ET-18-OCH3 enhances host defense mechanisms against tumors, its major antitumor action lies in a direct effect on cancer cells, inhibiting phosphatidylcholine biosynthesis and inducing apoptosis in tumor cells. Recent progress has allowed unraveling the molecular mechanism underlying the apoptotic action of ET-18-OCH3, leading to the notion that ET-18-OCH3 is selectively incorporated into tumor cells and induces cell death by intracellular activation of the cell death receptor Fas/CD95. This intracellular Fas/CD95 activation is a novel mechanism of action for an antitumor drug and represents a new way to target tumor cells in cancer chemotherapy that can be of interest as a new framework in designing novel antitumor drugs. ET-18-OCH3 and some analogues are pleiotropic agents that affect additional biomedical important diseases, including parasitic and autoimmune diseases, suggesting new therapeutic indications for these compounds.