(2) The redirection of phosphatidate utilization probably partly explains the phospholipidosis which is observed after prolonged treatment with high doses of many cationic drugs. The drugs stimulate the synthesis of acidic lipids which are subsequently transported to the lysosomes with the drugs. The situation is probably aggravated further by an inability of the lysosomes to degrade this abnormal substrate (Michell et al., 1976). (3) The cationic drugs which have been discussed generally interfere with membranelinked phenomena, such as movement, fusion, permeability, transport and receptor function (Brindley er al., 1975). Although these processes are not well understood, the turnover of acidic phospholipids seems to be involved. Cationic drugs have been shown to interfere with this turnover and to control the pattern of phospholipid which is synthesized. This in turn could contribute to the observed changes in membrane properties.