In a representative sample of 3,840 males examined for military service chromosome examination was made in those with testes equal to or less than 12 ml and those with a stature equal to or greater than 181 cm, as well as in males not recruited because of physical or mental disability. Testes equal to or less than 12 ml were found in 59 patients (1.45%). Three of these males had a 47,XXY karyotype (5.1%), the prevalence among the total sample of 3,840 being 0.78 per 1,000. Hypogonadal signs, except for gynaecomastia, which was only present in one patient, were found in the saem proportion as in 47,XXY males ascertained in institutions and clinics. The results of EEG investigations were alos similar to those found in psychiatric institutions. The intelligence level was comparatively low; none had an IQ above 100. The personality traits corresponded to those found in institutionalized Klinefelter males.