1. The low density fraction of the rainbow trout eggs which was obtained by centrifugation was separated into the partially defatted lipoprotein and its lipid moiety by ether treatment. This lipoprotein was divided into three components by electrophoresis. The slowest component in mobility was a lipoprotein similar to the slowest component of high density fraction previously reported.
2. The oil globule, characteristically rich in carotenoid and lacking in phosphorus, comprised mainly triglycerides, a small amount of cholesterol, cholesterol esters and a fairly amount of higher fatty acids.
3. The lipid of low density fraction contained triglycerides, cholesterol, cholesterol esters, higher fatty acids, phospholipids and trace amount of carotenoids.
4. The lipid moiety of high density lipoprotein consisted of about 50 per cent of phospholipids, in which lecithin, cephalin, sphingomyelin and lysolecithin were contained. The rest were triglycerides, cholesterol, its esters and higher fatty acids.
5. The fatty acid composition of the oil globule, the lipids of low density fraction and the lipids of high density fraction of the fish egg were determined.