THE CRIMINAL LIFE CURVE IS A SYSTEMATIC AND OBJECTIVE DESCRIPTION OF CRIMINAL BEHAVIOR BY AN INDIVIDUAL THROUGHOUT LIFE. THE CURVE UNDERGOES VARIOUS CHANGES AS IT IS INFLUENCED BY DIFFERENT ENVIRONMENTS. STUDIES USING MONOZYGOTIC TWINS HAVE REVEALED STRIKING SIMILARITIES BETWEEN THE CRIMINAL NATURES OF TWIN PAIRS IN TERMS OF THE TIMING, DIRECTION, AND REPETITION OF DELINQUENT AND AGGRESSIVE BEHAVIOR. ALTHOUGH FOR LONG PERIODS OF TIME VARYING CHILDHOOD ENVIRONMENTS SEEMED TO INFLUENCE THE CRIMINAL LIFE CURVES OF THE TWINS STUDIES, IN THE LONG RUN, THE TWIN WHO WAS IN A STATE OF LATENT CRIMINALITY CAME TO EMULATE THE TWIN PARTNER'S DELINQUENCY. WHILE BASED ON THESE FINDINGS IT SEEMS NATURAL TO ASSUME A PREDISPOSITION TO CRIMINALITY, IT IS CLEAR THAT SUCH A PREDISPOSITION DOES NOT PLAY AN EXCLUSIVE ROLE IN THE ETIOLOGY OF CRIME; A NUMBER OF OTHER FACTORS, SUCH AS BIRTH INJURY, POSTNATAL CEREBRAL INJURY AND DISEASE, PUBERTY CRISIS, ASSOCIATION, LATER MARRIED LIFE, WAR, ALCOHOL USE, AND SENILITY, MUST ALSO BE CONSIDERED. AN EARLY START IN CRIMINAL OR EARLY CHILDHOOD ENVIRONMENT ALONE ARE NOT SUFFICIENT PREDICTORS OF FUTURE CRIMINAL CONDUCT. GRAPHIC DATA ARE INCLUDED. (KBL)