In three groups of low birth weight (LBW) infants: full term, small-for-gestational-age (FT-SGA, N = 142); preterm, appropriate-for-gestational-age (PT-AGA, N = 47); preterm, small-for-gestational-age (PT-SGA, N = 20); and a reference group of FT-AGA infants (N = 185) the relationship between body weight, body length and head circumference and the presence of minor neurological dysfunction (MND) was studied. Non-caucasian and handicapped children were excluded from the analysis. Data were collected on behaviour and school achievement. The parameters of physical growth in the three LBW groups were reduced significantly compared to the FT-AGA group. In both preterms and full-terms body measurements were related to weight at term age; in the preterm groups no relation with gestational age at birth was found. MND was not related to body weight or length. In the group of FT severely growth retarded infants a relation was found between a skull circumference below the third centile and the presence of MND. Body measurements, behaviour at home and at school and school achievement were not related. The significance of severe intrauterine growth retardation for developmental disorders is emphasized. The data suggest a different aetiology and clinical significance of small head size for AGA and SGA born children.