The aim of the study was to examine the effect of the angiotensin-converting enzyme inhibitor perindopril on the development of atheroma in the cholesterol-fed rabbit. 2. The normal human carotid artery, like most large human arteries, has a preformed diffuse intimal thickening. To model this thickening, the right carotid artery of the 12-week-old rabbit had an expanded balloon catheter passed down it to remove the endothelium and partially damage the media. 3. Fourteen weeks after this operation, a myointimal thickening similar in almost all respects to the human intimal thickening had developed. The rabbits were then divided into six groups of six rabbits fed on: (i) a 1% cholesterol diet; (ii) a 1% cholesterol diet plus a hypotensive dose of perindopril (0.3 mg/kg per day); (iii) a 1% cholesterol diet plus a non-hypotensive dose of perindopril (0.01 mg/kg per day); (iv) a normal diet; (v) a normal diet plus a hypotensive dose of perindopril (0.3 mg/kg per day); and (vi) a normal diet plus a non-hypotensive dose of perindopril (0.01 mg/kg per day). 4. After 6 weeks of treatment the animals were sacrificed. There were ameliorating effects of both hypotensive and non-hypotensive doses of perindopril on the development of plaques, as determined by the area of intima covered by Oil Red-O-staining plaque and light microscopy. 5. Cell culture studies indicated that perindopril has no effect on smooth muscle proliferation, but increases collagen and non-collagen synthesis by smooth muscle cells and decreases their binding of the atherogenic lipoprotein beta-very low density lipoprotein (beta-VLDL).(ABSTRACT TRUNCATED AT 250 WORDS)