SYNOPSISA 10-year follow-up study is reported of 50 hypogonadal males, 34 of whom had the karyotype 47,XXY and 16 karyotype 46,XY. The social class of the former group was significantly lower and the frequency of criminal behaviour higher when compared with the latter group and the Danish male population. The frequency of mental illness was higher in the Klinefelter males with karyotype 47,XXY than in the remainder. The aetiology and pathogenesis of deviant mental development in the patient population and various aspects of their treatment are discussed.
