Characteristics attributed to carriers of various sex chromosome anomalies are tallness; reduction in the number of papillary crests and increase in the number of arches on fingertips; an inclination to mental disorders of various types, mental retardation, personality disturbances, criminal behavior; and minimal brain dysfunction. Many of the individuals with gonosomic anomalies come from the disadvantaged classes, broken homes, or homes with one parent missing. The sex chromosome abnormality would seem to predispose individuals to criminal activity only in the presence of adverse circumstances. One cannot, however, label a particular chromosome abnormality such as XYY, one which condemns individuals to criminal careers. The relative advantages and disadvantages of diagnosing such abnormalities by amniocentesis prior to birth must be weighed carefully. On one hand, an individual with abnormal chromosomes may be a potential danger to the public throughout his life, requiring constant surveillance. On the other, such an individual could become a scapegoat for society. As no treatment exists for such abnormalies, parents' knowledge of a child's abnormal condition might affect their attitude toward the child and contribute to his developmental difficulties. Medicolegal experts must consider how early diagnosis affects the rights of individuals and the interests of society and what will happen if individual and societal interests conflict. Tables and a 53-item bibliography are supplied. --in French.