The voltage-gated potassium channels (Kv) are partially responsible for the contraction/relaxation of blood vessels in response to changes in the Po(2) level. The present study determined the expression of Kvbeta1 and four oxygen-sensitive Kvalpha subunits (Kv1.2, Kv1.5, Kv2.1, and Kv9.3) in the ductus arteriosus (DA), the aorta (Ao), and the pulmonary artery (PA) in porcine neonates immediately after birth. We cloned three Kvbeta1 transcript variants (Kvbeta1.2, Kvbeta1.3, and Kvbeta1.4), Kv1.2, Kv1.5, and Kv9.3 from piglets. Three Kvbeta1 transcripts, Kv1.2, Kv1.5, and Kv9.3, encode predicted proteins of 401, 408, 202, 499, 600, and 491 residues. These Kv showed a high degree of sequence conservation with the corresponding Kv in human. Northern and quantitative real-time PCR (qr-PCR) analyses showed that Kvbeta1.2 expression was high in the DA and Ao but low in the PA. Kv1.5 expression was high in the Ao and PA but low in the DA. Expression of Kvbeta1.3, Kvbeta1.4, Kv1.2, Kv2.1, and Kv9.3 was low in these blood vessels. The inactivation property of Kvbeta1.2 against Kv1.5 was confirmed using Xenopus laevis oocytes. Our findings suggest that the molecular basis for the differential electrophysiological characteristics including opposing response to oxygen in the DA and the PA are partially due to diversity in expression of Kv1.5 and Kvbeta1.2 subunits. The high expression of Kvbeta1.2 and relatively low expression of Kv1.5 in the DA might be partially responsible for the ductal closure after birth.