Since previous studies have shown that persons with the 47/XYY chromosome variation are usually taller than those with normal chromosomes, a sample of 73 tall inmates (average height, 186 cm) from the Siegburg and Rheinbach correctional facilities and a control group of 35 tall university students (average height, 188 cm) were tested for chromosome types. The inmates' average age was 24.5 years, and that of the students was 25. The 47/XYY variation was found in two of the inmates. An autoradiographic examination of the DNA duplication patterns of the XYY chromosomes using 3 H-thymidin demonstrated a difference between the synthesizing behaviors of the two Y-chromosomes: one of the two synthesized the thymidin later than the other. This difference may be related to a difference in either the structure of the extra Y-chromosome or to its function. An examination of the two subjects revealed regressive testicle development in each. Furthermore, an examination of the chromosomes in each inmate's germ tissue showed that only normal chromosomes were present--a fact which suggests that the extra chromosome may be lost during germ production. Also, hormone levels were found to correspond to the regression in testicle development. Certain mental and family characteristics of these subjects have been found in similar studies of other samples: no members of the inmates' immediate families had committed crimes; the inmates' scores for practical intelligence were higher than their scores for theoretical intelligence; their emotional development was lacking; and they tended to avoid rather than to solve problems. A chromosome diagram, a table, and a reference list of 14 items are included. --in German.