The aim of the present pilot study was to investigate the impact of early intervention in the form of family-centred developmentally supportive care according to NIDCAP((R)) (Newborn Individualized Developmental Care and Assessment Program) on the development and behaviour of the child and on the mother-child interaction at 3 years of age. Two groups of very-low-birth-weight (VLBW) infants (< or = 1500 g) were studied. The control group (n=21) was born in 1990, i.e. prior to implementation of the NIDCAP. The intervention group, born in 1992-1993 (n=21), was subjected to formal NIDCAP observation once every 10 days. Development was assessed using the Griffiths' Developmental Scale II in conjunction with a neurological examination. Behaviour was assessed on the basis of a parental interview. Mother-child interaction was assessed according to the Parent-Child Early Relational Assessment Scale (ERA). There was no significant difference in motor development. The total developmental quotient (DQ) on the Griffiths' developmental scale was 109 (94-122) [median (range)] for the NIDCAP group and 108 (93-120) for the control group (n.s.). On the subscale hearing-speech, the intervention group scored 119 (72-157) and the control group 108 (84-130) (P=0.02). The total score with respect to the Behaviour Symptom Interview was 6 (0-20) for the NIDCAP group and 16 (0-54) for the control group (P=0.03). With respect to the mother-child interaction, there was a significant difference in the child cluster 'communication', the total score being 12 (11-13) for the NIDCAP group and 10 (9-13) for the control group (P=0.03). In conclusion, care of VLBW infants according to NIDCAP appears to have certain positive long-term effects on the child's behaviour and mother-child interaction.