Studies on interactions between physiologically active compounds and cell membrane components in Langmuir monolayers, which provide suitable models of biomembranes, can be considered as one of the crucial factors leading to the understanding of the mode of action of many drugs that act on membrane level. A good example of membrane-targeted drugs are synthetic analogues of lysophosphatidylcholine, generally named as antitumor lipids (ATLs), due to their anticancer properties. They have advantages over traditional cytostatics as they do not target DNA but cellular membrane. Apart from many studies on cell lines, little is known about the transport of ATLs to the cells, and it is still unclear which membrane components target drug molecules to the tumor cell membrane, sparing the normal cells. This review provides examples of the successful application of the Langmuir monolayer technique in getting insight into biological action and selectivity of representative ATL – edelfosine.