Macrophages form an important cell population involved in numerous immunological processes. Techniques which eliminate these cells, in order to permit 'in vivo' studies of their function are generally imperfect and for that reason we have developed a method using the liposome encapsulated drug dichloromethylene diphosphonate (Cl2MDP). The liposomes are ingested by the macrophages which are then destroyed following phospholipase-mediated disruption of the liposomal bilayers and release of the Cl2MDP. In the present review, technical details of the preparation of liposome encapsulated Cl2MDP are given, and applications of the technique are discussed.