The sexual histories of two hundred young English criminals, aged sixteen to twenty-one, were studied in relation to their criminal activity, physique, and some other factors. What kinds of criminal behavior had brought these young delinquents into the training school is not made sufficiently clear. The author seeks to correlate his data regarding age of onset and frequency of masturbation and heterosexual and homosexual activity with statistics from Kinsey and other sources; but his efforts are tentative and tenuous. He concludes, however, that 'criminals tend to start sexual behavior earlier and more vigorously but abandon it as their criminal career develops'.