Increases and decreases in the concentration or activity of vasopressin (VP) in mice result in facilitations and deficits in avoidance performance, respectively. An experiment was conducted to test the hypothesis that elevations in the central nervous system concentration of VP result from doses of d-amphetamine, strychnine sulfate and physostigmine known to induce facilitations of avoidance performance. An immunohistofluorescent technique was used to determine whether performance-facilitating doses of the three drugs elevated VP levels in a number of brain structures. A performance-facilitating dose of each of the three drugs was found to increase VP-like immunoreactivity in the dorsal raphe and lateral septum, but not in the substantia nigra, dentate gyrus or central amygdaloid nucleus.