The invention relates to a process for preparing substantially pure compacted L-tryptophan comprising roller compaction of L-tryptophan. It also relates to the compacted high-density L-tryptophan obtainable with such process, to the use of compacted L-tryptophan for preparing pharmaceutical compositions and to pharmaceutical compositions comprising compacted L-tryptophan as active ingredient. The process of the invention allows to remarkably increase the bulk density of L-tryptophan and, furthermore, by using compacted L-tryptophan, it is possible to considerably reduce the amount of excipients required to prepare pharmaceutical compositions comprising L-tryptophan as active ingredient.
