Hepatic detoxification capacities of three groups of infants aged about two were estimated using the [15N]methacetin elimination test, as well as standard serum parameters:1.Formerly hypotrophically born infants still too small for their age (n = 23)2.Patients suffering from severe liver diseases (n = 15)3.Patients without liver diseases (n = 14).17 of the infants of group 1 showed15N elimination rates as low as the rates of the liver-diseased patients of group 2. Compared to the infants of group 3, who had normal values, the findings reflect diminished hepatic monooxygenases activities in groups 1 and 2. On the other hand, the serum parameters of the infants of group 1 did not deviate from normal values estimated in group 3. Here only group 2 showed pathological values.Consequently, the [15N]methacetin test seems to be more sensitive in controlling hepatic parameters of growth retardations than the usual serum parameters used here. Further investigations have to answer the question to which proportion intrauterine malnutrition and postnatal effects, such as environmental living conditions, contribute to the retardation of liver function development in combination with growth retardation.