The incubation of milk, at 4 degrees C, from mothers of infants with breast milk jaundice (BMJ) is reported to result in significantly higher levels of free fatty acids (FFA) compared with milk from controls. Single milk samples collected under standard conditions were obtained from four mothers of infants with BMJ and 14 control donors matched for stage of lactation. Milk samples were analyzed for the concentrations of FFA, using thin-layer gas chromatographic techniques. In addition, serum total fatty acids were measured in mothers and infants. The concentrations of FFA increased after storage of the milk from both the jaundiced and control groups. No differences were observed in the composition of milk FFA before or after incubation, when respective values were compared between these two groups. Similarly, no differences were detected in serum total fatty acids in either infants or mothers. The observation that increased levels of FFA in milk are associated with BMJ was not confirmed.