The aim of the study was to test experimentally whether vagal afferent pathways are involved in the reflex regulation of jejunal fluid absorption. Acute bilateral cervical vagotomy led to an increase in net jejunal fluid absorption rate, an effect which was abolished by previous division of the splanchnic nerves. Selective division of the right cardiac branch of the vagal nerve induced an increase in fluid absorption similar to that elicited by truncal cervical vagotomy. Afferent stimulation of the right cardiac nerve at frequencies within the physiological firing range for unmyelinated C-fibre afferents induced an inhibition of net fluid absorption. Based on these findings, we propose a reflex pathway containing a non-myelinated vagal afferent branch originating from cardiopulmonary receptor endings, and an efferent sympathetic branch reaching the jejunum via the splanchnic nerves. Such a pathway might be of physiological importance in extracellular volume control by regulating the rate of fluid transport across the intestinal mucosa.