Objective: Postinterventional irradiation is a new therapeutic concept in the prevention of restenosis. The liquid β-emitter Rhenium-188 allows endovascular brachytherapy using a conventional balloon catheter without the problem of centering the radiation source. In an animal model of restenosis the feasibility and the dose dependent effect of intravascular brachytherapy with a Rhenium-188 filled balloon catheter was investigated. Methods: In 68 male New Zealand White rabbits after endothelial denudation of the right common carotid artery with a Fogarty catheter, endovascular irradiation was performed with a Rhenium-188 filled 3.0-mm balloon catheter using different dosages (0, 7.5, 15, 30, 45 and 60 Gy at the surface of the vessel). Then 4 weeks after the intervention the vessels were excised and histologically analyzed. Results: Whereas at 7.5 Gy the intimal area (median [first quartile; third quartile]) did not differ significantly from the control (0.46 mm² [0.33 mm², 0.75 mm²] vs. 0.49 mm² [0.34 mm², 0.66 mm²]), neointimal hyperplasia was decreased significantly at 15 Gy (0.15 mm² [0.04 mm², 0.17 mm²]) and 30 Gy (0.07 mm² [0.04 mm², 0.10 mm²]), and completely inhibited at the highest dosages (45 Gy: 0 mm² [0 mm², 0.04 mm²]; 60 Gy: 0 mm² [0 mm², 0.01 mm²]). Conclusions: Catheter transmitted endovascular irradiation with the liquid β-emitter Rhenium-188 after vascular injury is feasible and effectively reduced neointimal hyperplasia in hypercholesterolemic rabbits. A significant reduction of the neointimal formation could be found already at a radiation absorbed dose of 15 Gy at the vessel surface. Following a surface dosage of 45 Gy the proliferative response to the vessel injury is almost completely abolished. (C) 2001 Elsevier Science B.V.