Early workers studying children because of persistent delinquency concluded that the child's inability to make relationships was the central core from which all other behaviour disturbances arose. The long term effects of institutionalization and repeated moves from foster mother to foster mother, it was asserted, were basic in any consideration of aetiology. The difficulty of treating these patients and the permanency of ill-effects was emphasized. In his well-known World Health Organization Bulletin, Bowlby (1951) concluded ‘on the basis of this varied evidence it appears that there is a very strong case indeed for believing that prolonged separation of a child from his mother (or mother substitute) during the first five years of life stands foremost amongst the causes of delinquent character development’. Whilst the practical conclusions of this publication led to a remarkable change in outlook and improvement in the institutional care of children, his theoretical conclusions have drawn heavy fire. Andry (1960) directed attention to the ‘defective role frequently played by the father and not only that of the all-too-often mentioned mother’. Wootton (1959, 1962) regards as an unproven hypothesis ‘that maternal deprivation leads to life-long damage and is a major factor in criminal behaviour’. She argues that Bowlby has overstated the case for the separation experience itself, without due regard to the conditions the child has come from or goes to, and has given scant recognition to hereditary factors. Wootton notes that relatively few investigations have traced the fortunes of the maternally deprived after adolescence, let alone throughout life, and hence there is no definitive proof that the damaging effects of the separation experience are irreversible. Further, the maternal separation hypothesis relates to only a minority of the delinquent population (the ‘affectless psychopath’) and there is no experience of the general population at large of comparable infantile experiences. A review of the recent literature (Lancet, 1966, British Medical Journal, 1967), indicates that various investigations into the long term effects of childhood parental deprivation and bereavement in the causation of adult mental ill health and behaviour disturbance have yielded inconclusive results. Whilst this state of affairs suggests that further studies are necessary to detect consistent patterns of parental deprivation, these patterns by themselves may not indicate precise modes of aetiology, but when taken into consideration with other objective data of family background may yield the development or refutation of hypotheses regarding various determinants of psychiatric disorder. In the light of these contemporary uncertainties we have re-examined the hypothesis that early adverse experiences are related to subsequent delinquency and criminality. By statistical procedures we examined two prison populations, one consisting of short term male first offenders of less serious crime, and the other of male recidivists and those convicted of serious crime. Various groups from the general population at large have been incorporated to act as the control group.