AbstractEncapsulated health food oils such as fish oils are readily available in health food stores, pharmacies, and supermarkets. They are popular in the United States as well as in the European countries. However, such oils, because of their high degree of unsaturation, are easily oxidized and form complex mixtures of high molecular weight oxidation products. The present work reports the application of high‐performance size exclusion chromatography to the determination of these materials in encapsulated fish oils. Of the six samples studied, five showed from 1–10% of dimeric triacylglycerols and one contained 6.3% trimeric triacylglycerols and 3.1% oligomeric triacylglycerols. Further investigation of this sample with silicic acid chromatography indicated that it contained a total of 36.3% polar material.