The relationship between essential fatty acid (EFA) deficiency and disturbance of prostaglandin (PG) biosynthesis was studied in children after radical operation for extrahepatic biliary atresia (EBA). In addition, to investigate the method for treatment of postoperative EFA deficiency and disturbance of PG biosynthesis, the serum fatty acid and plasma PG levels were determined before and after supplementation of an EFA-rich powder (38 g of linoeic acid per 100 g of powder) through Suruga II enterostomy. Before administration of the EFA-rich powder, linoleic acid, arachidonic acid, PGE1, and PGF2αlevels were significantly lower in both good bile excretion and poor bile excretion groups than in the control group. After administration, linoleic acid and PGE1levels significantly increased in the good bile excretion group as compared with the preadministration values. These results suggest that the supplementation of EFA-rich powder is an effective treatment for linoleic acid deficiency and disturbance of PGE1biosynthesis in postoperative EBA patients.