The authors give a statistical analysis of 107 men in the state Prison at Charlestown all of whom had been convicted of a felony, the shortest sentence of which was two and a half years. The most important conclusion that they come to is, that the present temporary institutional care of delinquents does not effectually cure the individual or protect society, and that the medico-sociological study of individual delinquents forms the most rational basis for treating the individual and for formulating methods of care, and is inadequately applied.