In bilaterally nephrectomized rats fatty acid synthesis (incorporation of 3H from 3H2O into fatty acids by the liver) and triacylglycerol (TG) secretion by the liver (Triton method) were investigated 24 h after surgery. Starved and fed rats were employed. In uremic rats fatty acid synthesis occurs at a normal rate; prevention of acidosis during uremia by bicarbonate treatment has no influence on lipid synthesis. Following intravenous injections of Triton WR 1339 the TG plasma levels are considerably lower in uremic rats than in corresponding controls. As the plasma volume is significantly higher in uremic animals, there is only an insignificant decrease in the absolute TG secretion rate in these animals. The removal of TG from the blood to the tissues in severely reduced in uremia with acidosis. The normal rates of fatty acid synthesis and nearly normal rates of TG secretion may, therefore, be considered as permissive factors for the development of uremic hypertriglyceridemia. The lesser degree of hypertriglyceridemia in uremia without acidosis is only caused by the better removal of TG from the blood (as could be demonstrated earlier). Fatty acid synthesis and TG secretion do not play any role in this case.