Stool composition was studied in 10 newborn infants following (a) a modified milk formula (Cow & Gate Premium) and (b) a high energy formula [104 kcal (435 kJ) per 100 ml] in which the additional energy was provided in the form of 10 per cent Caloreen. The only significant difference in stool composition in the Caloreen-fed babies was a lower sodium concentration. The results suggest that the high energy diet did not produce diarrhoea or other changes in the stool composition which might have an adverse effect on the infant.