While regional plasma concentrations of the endocrine hormones atrial and brain natriuretic peptide (ANP and BNP) have been studied, there are few reports of regional changes in the largely paracrine C-type natriuretic peptide (CNP) and its amino terminal fragment NT-CNP. Accordingly, we have performed trans-organ arteriovenous sampling for measurement of plasma ANP, BNP, CNP and NT-CNP in anesthetized sheep before and after induction of experimental heart failure. ANP and BNP plasma concentrations are sourced from a single organ (the heart) and are subject to substantial extraction across most tissue beds. In contrast, our data demonstrate that multiple tissues including liver, heart, hind limb and kidney contribute to circulating CNP. Given that arteriovenous gradients for NT-CNP were similar, this is likely to represent de novo secretion. Circulating levels of CNP and NT-CNP were raised in heart failure but to a much lesser degree than ANP and BNP. There was no evidence of net extraction of CNP or NT-CNP across any tissue bed.