A description of a new system for the complete separation of lipid classes in natural mixtures by two-dimensional chromatography on thin layers of silica gel impregnated with ammonium sulphate to improve separations. For quantitative analysis an amount of 1 mg. of total lipids is chromatographed, and the lipid classes resolved are then determined by gas chromatography of their constituent fatty acids with added internal standard. The patterns of the constituent fatty acids of the individual lipid classes are obtained simultaneously. -- AATA