DHA is a typical n-3 polyunsaturated fatty acid (n-3 PUFA), and numerous epidemiological and clinical studies have shown that its intake exerts beneficial preventive effects against various cardiovascular diseases. Although possible vascular relaxation induced by DHA seems to be a mechanism underlying its cardioprotective effects, few pharmacological studies have been reported to evidence this idea. In this regard, we found that in the isolated rat thoracic aortae and mesenteric arteries, DHA shows acute and selective suppressive effects against prostanoid receptor-mediated contraction, which may partly underly its cardiovascular protective effects. In this study, we examined the possibility that DHA also shows selective suppressive effects vs. prostanoid receptor-mediated contractions in coronary and cerebral arteries. In both porcine coronary and cerebral arteries, DHA (~3 × 10⁻⁵ M) inhibited U46619- and PGF_2α-induced contractions more potently than high (80 mM)-KCl-induced contraction. These findings suggest that DHA strongly and selectively suppresses prostanoid receptor-mediated contraction in both coronary and cerebral arteries, which suggests that this n-3 PUFA is also significant in preventing the occurrence of coronary and cerebral spasm due to contractile prostaglandins.