The effect of butylamine, pentylamine and hexylamine on spontaneous locomotor activity of mice was evaluated in the presence or absence of drugs affecting monoaminergic neurons. Pentylamine and hexylamine produced similar effects (stimulation after low, inhibition after high doses), while butylamine action was weak. Depression of locomotor activity produced by combined treatment with alpha-methyl-tyrosine, reserpine and dopa was counteracted by pentylamine and hexylamine; they did not produce such an effect in the absence of dopa. The amines did not displace 3H-spiperone specifically bound to striatal membranes.