Multiple sclerosis (MS) is a chronic, demyelinating disease of unknown origin. Sophisticated analytical methods have made it possible to measure small biologically active molecules at low endogenous levels, and understand their role in the network of other biologically active compounds actively involved in inflammatory and neurodegenerative processes. Evidence is accumulating as concerns the disturbances of the kynurenine pathway and redox changes in MS. A new promising metabolite of the kynurenine pathway seems to beneficially influence experimental allergic encephalomyelitis. More clinical evidence is needed to prove the role of kynurenic acid analogues and/or enzyme inhibitors as potential medications in MS in the future. Various compounds have been shown to be important in the pathophysiological processes of the disease and are targets for pharmaceutical intervention.