Ten premature infants with a mean gestational age of 29 weeks (range, 27-32) and a mean birth weight of 1,294 g (range, 930-2,300) and without complications at birth were studied during the first 14 days after birth. Their breast milk intake was recorded and the carnitine content determined in each daily portion. During the first week, the daily mean carnitine intake was low and increased to 6-7 mumoles/kg and day during the second week. Breast milk carnitine concentration ranged from 17 to 148 mumoles/L. Plasma carnitine and its derivatives did not change during the observation period. No relationship was found between the individual cumulative breast milk carnitine intake and total plasma carnitine levels or between carnitine and its derivatives and nonesterified fatty acids or 3-OH-butyrate. The urinary carnitine excretion, in millimoles of carnitine per mole of creatinine, was higher during the second week. In other studies, declining plasma carnitine levels have been observed in premature infants on total parenteral nutrition. The results from this study indicated that premature infants without complicating disorders were able to maintain their plasma carnitine levels.