The influence of an increasing dose of the vasopressin-like peptide DGAVP (desglycinamide-arginine-vasopressin) on memory was investigated in two groups of ten healthy male volunteers to provide information about the hypothesis of improvement of memory by vasopressin. At the same time we evaluated the effect of DGAVP on mood, alertness or sleepiness in a double-blind placebo-control design. The treatment group received at 9.15 a.m. intranasally a daily increasing dose from 0.1 mg at day 1 to 10.0 mg at day 5. DGAVP did not significantly affect any measure of memory or alertness. DGAVP did, however, produce a significant increase in concentration level and mood. The results of the present study provide no support for the vasopressin theory of memory improvement; rather, the results direct the attention to attention modulating effects.