Knowledge gained from research with plant tissues has been of considerable importance in defining the biochemistry of Refsum's Disease and the function of hypolipidemic drugs in the treatment of hyperlipidemia. Reference is made to the discovery and elucidation of an Alpha-oxidation system as related to Refsum's Disease and the discovery of Beta-oxidation enzymes in plant microbodies in 1969 and the discovery of a similar system in liver peroxisomes on treatment of animals with hypolipidemic drugs. It is proposed here to examine in detail the molecular structure of two systems in plant tissues: the first, the palmitoyl ACP synthetase (System I) and the second, the palmitoyl ACP elongase (System II). In plants, these occur in organelle systems in sharp contrast to the cytosolic localization of animal fatty acid synthetases. knowledge gained from these studies will complete the information of the synthetases already examined in eubacteria and in animal tissues. It is also proposed to reexamine animal fatty acid synthetase by using gentle isolation techniques to determine if in animals, a fragile organelle is indeed the actual site of synthesis. If so, the physiology and biochemistry of animal lipid biosynthesis would need considerable re-evaluation.