Fish oil fatty acids (FOFA) were analyzed in fresh liver tissue and in subcutaneous and omental adipose tissue obtained from 5 patients who underwent partial hepatectomy. FOFA were also determined in plasma from 5 patients and in 10 healthy subjects. There was a high content of FOFA in the liver phospholipid (PL) fraction (twice that in our previous autopsy study) suggesting that these surgery patients had a hepatic FOFA content of at least 25g. In plasma, FOFA was predominantly found in the PL of high density lipoprotein (HDL) and partly in the PL of other lipoproteins. Since these lipoproteins are produced by the liver, the present findings indicate the role of the liver not only in storage but also in the utilization of FOFA to form the biologically important surface PL component of circulating lipoproteins.