Preclinical and clinical data suggest that lipid abnormalities are involved in the pathogenesis of schizophrenia. The arguments in favour of this theory come from assessments of reduced tissue levels of essential fatty acids, altered phospholipases A2 enzyme activity and genetic studies on polymorphisms of their genes, increased brain levels of apolipoproteins D and L, increased turn-over of brain phospholipids in phosphorus-31 magnetic resonance spectroscopy, evaluation of the niacin flush test as a possible diagnostic marker and promising results of treatment trials using supplementation with eicosapentaenoic acid preparations, although some inconsistencies need further examination.