[Catamneses of YY carriers in prison]

Among the 700 inmates of a big Austrian prison 5 cases of XYY caryotype were detected by means of the Quinacrinfluorescence method and subsequent lymphocyte culture. Keeping in mind that, if at all, only a small amount of criminal behavior may be explained by chromosomal factors three hypotheses about possible links between the XYY abnormality and criminal behavior are discussed in this paper. 1. the connection is a spurious one, as both criminal behavior and the XYY caryotype are more frequent in a working class population without being necessarily linked causally. 2. criminal behavior may be a consequence of the bodily abnormalities connected with the XYY abnormality. 3. the XYY type may contribute to criminal behaviour by acting upon neuro-endocrinological structures.