['To investigate the effects of oral administration of all-trans retinoic acid (ATRA) on inhibition of intimal thickening after balloon angioplasty in the rabbit iliac artery atherosclerotic model.', 'Iliac atherosclerosis was induced in 24 rabbits, and balloon angioplasty was performed. At angioplasty, 24 rabbits were randomly divided into four groups (n = 6 per group): Group 1: controls not receiving oral ATRA administration; Group 2: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning 1 week prior to angioplasty and continuing for 4 weeks; Group 3: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning immediately after angioplasty and continuing for 4 wk; Group 4: receiving oral ATRA (0.6 mg.kg-1.d-1) administration beginning 1 wk after angioplasty and continuing for 4 wk. Values of cross-sectional area, ratio of intimal/medial area and thickness were determined by a computer-based morphometric system, and cell proliferative activity was assessed by 3H-thymidine incorporation.', 'Both the cross-sectional area and the ratio of intimal/medial area and thickness were significantly reduced by ATRA administration compared with control group (P < 0.01). The inhibitory effect is less potent when ATRA is administered 1 week before angioplasty. The ATRA inhibitory effect when administered 1 week after angioplasty is not different significantly form that when administered immediately after angioplasty. The 3H-thymidine incorporation was also decreased in ATRA-treated rabbits compared with controls (P < 0.01).'] Does all-trans retinoic acid reduce intimal thickening after balloon angioplasty in atherosclerotic rabbits?