SYNOPSISA study of four 47XYY subjects and their families is reported. These subjects were all exceptionally tall; were mostly of good intelligence and from intelligent families; and all had a history of delinquency or criminality, although they came from respectable homes. Evidence is presented, however, to suggest that both adverse environmental influences and constitutional factors other than their supernumary chromosomes nevertheless operated in these cases, indicating that their deviant behaviour need not be directly related to their chromosomal abnormality. The implications of these findings are discussed with respect especially to their bearing on conclusions drawn in the literature on the XYY syndrome.

A critical and comprehensive review of the major sex chromosome disorders. The introduction briefly outlines the cytogenetic background to these disorders and refers to earlier reviews. The paper then reviews the clinical and psychiatric aspects of the various chromosome disorders. Male and female phenotypes are dealt with separately, with emphasis on psychological and behavioural manifestations including antisocial behaviour. Medico-legal implications are also reviewed, as are the implications for research.

Psychiatrists in clinical practice are not infre quently asked for advice about the risk to offspring or other relatives of their inheriting a psychiatric disorder. In the overwhelming majority of cases this