73 (34%) of 213 inborn, long term survivors with a birthweight less than 1500 g showed characteristics of Attention Deficit Disorder (ADD) during psychological testing at 2 years of age corrected for prematurity. Agreement on the diagnosis of ADD made by the paediatrician and psychologist in separate examinations was statistically significant. Children with ADD differed from those with normal behaviour on a large number of neonatal variables which were reduced to the following five on stepwise discriminant function analysis: necrotizing enterocolitis, bronchopulmonary dysplasia, major apnoeas requiring bag and mask resuscitation, duration of feeding on intravenous fat and weight percentile at discharge. These neonatal variables correctly classified 69% of children into their actual behaviour group at 2 years. On psychological testing, children with ADD had a significantly lower mental score on the Bayley Scales of Infant Development and were found on their paediatric/neurological examination at 2 years to have a significantly smaller head circumference, more tone disorders, poorer visual tracking and visual motor co-ordination, poorer gross and fine motor co-ordination and significantly more minor physical and neurological disabilities than normally behaved children. The behaviour of very low birthweight infants during formal psychological testing at 2 years is a potent indicator of past neonatal experience and current neurodevelopmental status.