We measured CSF and serum concentrations of biogenie amines (DA, NE, E, and serotonin), some of their metabolites (HVA, 5-HIAA, and IAA) and tryptophan in 11 narcoleptic, 11 idiopathic hypersomniac, and 11 control subjects. The concentrations of DA and IAA, a metabolite of tryptamine, were significantly decreased in the CSF of both groups of hypersomniacs. Both DA and tryptamine are found in highest concentrations in the striatum, which is probably involved in the physiopathology of hypersomnia.