Increased plasma homocyst(e)ine is strongly correlated with occlusive arterial diseases. A series of different hypotheses have been reported including involvement of free oxygen radicals and therefore oxidative stress. We determined plasma homocyst(e)ine and homocysteic acid levels after oral low dose homocysteine thiolactone administration to rats for a period of six weeks. Plasma levels of homocyst(e)ine and triglycerides were significantly elevated in the group fed homocysteine thiolactone. GC/MS determination of ketone body formation showed that the underlying mechanism for the increase of triglycerides seems to be inhibition of fatty acid oxidation. Homocysteic acid was detected in the experimental group exclusively. The present study showing a homocyst(e)ine correlated increase of plasma triglycerides by the inhibition of fatty acid oxidation may well propose an additional role of triglycerides for vascular pathology. The presence of homocysteic acid in the experimental group only would support the free oxygen radical hypothesis for the development of vascular changes but homocysteic acid as a potent neurotransmitter could play an independent role in the pathogenesis.