The degradation of the vasopressin analogue dDAVP was studied by reversed phase high-performance liquid chromatography (HPLC) after incubations in pancreatic juice and intestinal mucosa homogenates. dDAVP remained stable in pancreatic juice for a period of 60 min. while the parent hormone arginine vasopressin (AVP) was completely degraded within 5 min. In intestinal mucosa homogenates dDAVP was degraded with half-lives of 9 min. (fast phase) and 161 min. (slow phase), about four times slower than AVP. By amino-acid analysis it was confirmed that the metabolite [Mpa1, Des-D-Arg8-Gly9 NH2]-vasopressin was gradually produced. No other breakdown products were observed. These findings may be of value for the further development of more stable peptide analogues which may be effective upon oral administration.