A sensitive flow injection analysis using luminol/peroxidase chemiluminescence was developed for the determination of choline-containing phospholipids in serum. Flow injection manifold was composed of two channel system with an enzyme column, in which phospholipase D was immobilized together with choline oxidase. The serum sample (5 microliters) was pretreated by Extrelut column (diatomite column) extraction with chloroform-methanol (95:5). The extract (20 microliters) was injected into a sample carrier at 38 degrees C and passed through the enzyme column, which converted phospholipid to choline and subsequently to hydrogen peroxide. Produced hydrogen peroxide was monitored by measuring the chemiluminescence intensity of luminol/peroxidase system at 5 degrees C. The response was linear against the amount of phospholipids ranging from 2 to 2000 pmol/test, and the relative standard deviation was less than 2%. In the determination of phospholipids in the serum, a correlation coefficient (r) between 4-aminoantipyrine/phenol and the proposed methods was found to be 0.983 (Y = 1.035X-6.2). The throughput rate was 15 samples/h.