Family Environment and Delinquency, which Professor Sheldon Glueck and I completed in March 1961 and which is scheduled for publication in April 1962, grew out of two prior studies—Unraveling Juvenile Delinquency and Physique and Delinquency. The new work is a companion volume to Physique and Delinquency, which was an analysis of the differences in the psysiologic-psychologic characteristics between the 500 delinquents of Unraveling and a matched sample of 500 nondelinquents of four constitutional types—mesomorphic, endomorphic, ectomorphic, and balanced. Physique and Delinquency served as a preliminary to determining the impact of these differences not only on the delinquency of boys of the various physique types but also on the response of the delinquents of each physique type to certain environmental (largely familial) pressures. The 67 characteristics studied are appended to this paper (Appendix A). They encompass physical and neurological conditions, constituents of intelligence, emotional dynamics, appetitive- aesthetic tendencies, and personality orientation.