The possible role of an antidiuretic hormone analogue, DDAVP (1 deamino-8-D-arginine vasopressin), in intravenous urography has been studied. The minimum effective dose of intravenous DDAVP in normal hydrated subjects was shown to be 2 ng/kg. During intravenous urography in fluid restricted subjects, a dose of 1 microgram DDAVP was necessary to reduce significantly the urine flow rate after contrast medium injection. Although the mean pyelographic score after DDAVP was increased, the differences observed were not statistically significant. The possible reasons for this finding are discussed.