Tetra-iso-propyl 2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethyl-1,1-diphosphonate (CAS 126411-13-0, SR-9223i) is a member of a new class of compounds with multiple antiatherosclerotic activities. This report not only describes the cholesterol-lowering properties in four species of animals fed normocholesterolaemic diets but also reductions in lipid deposition in the arteries of cholesterol-fed New Zealand white rabbits following the administration of SR-9223i. Plasma cholesterol concentrations were reduced in mice by 27% (200 mg/kg/day administered in the diet for 10 days), in hamsters by 33% (200 mg/kg/day administered in the diet for 8 days), in dogs by 16% (25 mg/kg/day p.o. for 28 days) and 23% (75 mg/kg/day p.o. for 28 days) and in monkeys by 22% (25 mg/kg/day p.o. for 28 days). Further, the deposition of cholesterol, especially in the esterified form, in the aortae of cholesterol-fed New Zealand white rabbits was inhibited by SR-9223i (50 and 100 mg/kg/day p.o.). At the higher dose, the cholesteryl ester content of the aorta was half that of control animals. SR-9223i, at both doses, also inhibited the accumulation of cholesterol in the liver. SR-9223i has been shown to suppress HMG CoA reductase activity, inhibit ACAT activity and prevent lipid oxidation. These activities, demonstrated in vitro, have now been shown to translate into lipid lowering and antiatherosclerotic activities in vivo.