The simultaneous quantitation of PC, PE, CDP—choline and.CDP—ethanolamine has been performed by highperformance liquid chromatography of purified rat brain extracts. The water—soluble intermediates of the phosphoglyceride biosynthesis were extracted from the rat brain by homogenization in 1 M PCA and purified by chro¬matography on neutral alumina and Dowex l. This procedure remove almost all of the UV—contaminating substances and inorganic phosphate, which interfere in the analytical chromatographic process. The high performance liquid chromatography was carried out using the styrene type Aminex A-14 resin. The elution was performed for 5 min with 0.1 M 2—amino-2—methyl-1—propanol, 0.02 M NaCl, pH 10.3 buffer, and then with 0.1 M 2—amino-2-methy-1—propanol, 0.17 M NaCl, pH 11.0 solution, until the end of the run. Satisfactory separations of PC, PE, CDP—choline and CDP—ethanolamine were achieved within 30 min. 5’-CMP can also be dosed. The cytidine contain¬ing compounds have been detected and quantified by UV absorption at 280 nm, while PC and PE by phosphorus determination in the chromatographic fractions. The method allows the quantitative determination in subgram amounts of wet tissue.