Disturbances in Tryptophan metabolism play a crucial role in multiple sclerosis (MS). Exercise is suspected to counteract the progress of MS and its side effects. Current research suggests alterations of Tryptophan metabolism in healthy individuals in response to exercise. We investigated the influence of acute aerobic exercise and training on Tryptophan metabolism in 57 inpatients with relapsing remitting ((RRMS) n=33) and secondary progressive ((SPMS) n=24) MS. Serotonin increased after training, whereas the kynurenine pathway was only activated in persons with RRMS. Further research is warranted to investigate whether these changes are associated with clinical measures (e.g. depressions and immune function).