This book describes and examines five psychological systems for classifying adult male prison inmates: 1) Warren's I-level; 2) Megargee's MMPI-Based Criminal Classification System; 3) Hunt's Conceptual Level; 4) Quay's Adult Internal Management System; and 5) the Jesness Inventory Classification System. It also presents psychometric data on the reliability and validity of each system and illustrates different adjustment patterns of prison inmates.