Lipoidal material binds to bilirubin in vitro. It has been suggested that its use may augment the bilirubin binding properties of albumin giving further protection against kernicterus. In vitro studies of the effects of bilirubin-albumin binding of Intralipid, a commercially prepared soy bean fat emulsion for use in intravenous feed in human parenteral nutrition, were carried out in human serum albumin, human plasma and red blood cells. Utilizing a modified Sephadex G-25 elution technique, it was shown that in a prepared bilirubin-albumin solution, Intralipid in concentrations of 0.25 - 1.00 gms% binds bilirubin only after the primary albumin binding site is saturated with bilirubin. This effect was not reproducible in artificially jaundiced human adult plasma. Intralipid does not alter the dynamic equilibrium between the bilirubin in plasma and red blood cells at bilirubin-alburain molar ratios of <1. At molar ratios of >2 the fat competes with the red cell membrane for bilirubin. Thus, although Intralipid itself does not have any adverse affects on bilirubin-albumin binding, it does not provide any beneficial effect in the prevention of kernicterus. It is suggested that the in vivo metabolism of fat which leads to an increase of free fatty acid in plasma, may have a deleterious affect on bilirubin-albumin binding and as such may be potentially dangerous.