The quality and digestibility of the natural food of Oreochromisrnniloticus in Lake ZiHay, Ethiopia, ~/aS studied for a period of one year,rnOctober, 1988 to September, 1989. The stomach and rectal contents of 956rnfishes I'/ere analyzed for total organic matter, protein, lipid, carbohydraternand energy. Different forms of inorganic nitrogen and or tho-phosphate in thernI-later 11ere also determined to assess if there is any relationship I-lith therncomposition of the diet.rnTotal organic matter (55.7% D.