Kynurenine is a metabolite of the tryptophan-nicotine-amide-adenine-dinucleotide pathway. Recent preclinical and clinical data suggest that kynurenine and its metabolites (kynurenic acid, quinolinic acid) may play important role in the pathogenesis of neurological and other disorders (Huntington's disease, epilepsy, hypoxia, ulcus, hepatic and infectious diseases). Experimental data and theoretical considerations suggest that modification of kynurenine metabolism and influence of the concentrations of kynurenine metabolites may be useful therapeutic strategies in treatment of several disorders. This review is a summary of the pathobiochemical mechanisms and possible therapeutic strategies.