Abstract. By using a specific radioimmunoassay for 1-deamino-8-D-arginine vasopressin (DDAVP), plasma concentrations were measured in rabbit plasma at various times after intra-gastrointestinal injections. Five anatomically distinct regions were employed to administer the peptide, namely: the stomach, the duodenum, the mid-part of the ileum, the ileo-coecal junction and the mid-part of the colon. In each case immunoreactive DDAVP could be demonstrated in plasma. The highest concentrations were observed after duodenal and ileocoecal administration. Absorption was rapid; peak levels were reached after 10–20 min.