L-tryptophan is accumulated by slices of seven regions of the rat brain in a saturable, energy-depending fashion, with K(m)-values ranging from 53 to 142 muM. The maximal number of L-tryptophan accumulating sites differs only by about two-fold for the brain regions investigated. The regional distribution of the high-affinity L-tryptophan uptake does not correlate with the amount of serotonin synaptosomal uptake and apparent receptor binding. It is assumed that a specific role of the L-tryptophan uptake system within the serotoninergic system in the brain is questionable.