Objective To evaluate the possible vascular effects of an environment carcinogen benzo(a)pyrene (BaP). Methods The cytotoxicit of BaP and rat liver S9 (0.25 mg/mL)-activated BaP were examined by MTT assay. Thoracic aortic rings were dissected from Sprague-Dawley rats. Contraction of aortic rings was induced by 60 mmol/L KCl or 10 -6 mol/L phenylephrine (PE) in an ex-vivo perfusion system after BaP (100 μmol/L) incubation for 6 h. [Ca 2+ ] i was measured using Fluo-4/AM. For in-vivo treatment, rats were injected with BaP for 4 weeks (10 mg/kg, weekly, i.p.). Results BaP (1-500 μm) did not significantly affect cell viability; S9-activated BaP stimulated cell proliferation. BaP did not affect the contractile function of endothelium-intact or -denuded aortic rings. BaP did not affect ATP-induced ([Ca 2+ ] i ) increases in human umbilical vein endothelial cells. In BaP-treated rats, heart rate and the number of circulating inflammatory cells were not affected. Body weight decreased while blood pressure increased significantly. The maximum aortic contractile responses to PE and KCl and the maximum aortic relaxation response to acetylcholine were significantly decreased by 25.0%, 34.2%, and 10.4%, respectively. Conclusion These results suggest, in accordance with its DNA-damaging properties, that metabolic activation is a prerequisite for BaP-induced cardiovascular toxicity. Objective To evaluate the possible vascular effects of an environment carcinogen benzo (a) pyrene (BaP). Methods The cytotoxicit of BaP and rat liver S9 (0.25 mg / mL) -activated BaP were examined by MTT assay. Thoracic aortic rings were dissected from Sprague-Dawley rats. Contraction of aortic rings was induced by 60 mmol / L KCl or 10 -6 mol / L phenylephrine (PE) in an ex-vivo perfusion system incubated with BaP at 100 μmol / L for 6 h. [Ca Rats were injected with BaP for 4 weeks (10 mg / kg, weekly, ip). Results BaP (1-500 μm) did not significant affect BaP did not affect the contractile function of endothelium-intact or -denuded aortic rings. BaP did not affect ATP-induced ([Ca 2+] i) increases in human umbilical vein endothelial cells In BaP-treated rats, heart rate and the number of circulating inflammatory cells were not affected. Body weight decreased while The maximum suggest aortic contractile responses to PE and KCl and the maximum aortic relaxation response to acetylcholine were significantly decreased by 25.0%, 34.2%, and 10.4%, respectively. Conclusion These results suggest, in accordance with its DNA-damaging properties, that metabolic activation is a prerequisite for BaP-induced cardiovascular toxicity.