THE CASE STUDIES FOCUS ON THE FOLLOWING FACTORS: THE PERSONALITY OF THE KILLED PARENT; THE KILLED PARENT'S IMPACT ON THE FAMILY IN GENERAL AND ON THE PERPETRATOR IN PARTICULAR; THE SURVIVING PARENT'S PERSONALITY; THE RELATIONSHIP BETWEEN THE PARENTS; FAMILY LIFE BEFORE AND AFTER THE KILLING; SOCIETAL RESPONSES TO THE FAMILY; AND THE PSYCHOSOCIAL FATE OF THE PERPETRATOR. THE KILLINGS DESCRIBED WERE DELIBERATE, GOAL-DIRECTED, AND IN A CERTAIN SENSE ADAPTIVE. THE KILLED PARENT GENERALLY WAS A SADISTIC PERSON WHO TORTURED THE ENTIRE FAMILY. LIVING IN DREAD OF THE SADISTIC PARENT THE FAMILY WAS INCAPABLE OF LEADING A NORMAL LIFE. THE PERPETRATORS TENDED TO BE PARTICULARLY AFFECTED, EITHER BECAUSE THEY WERE THE PRIMARY TARGET OF THE PARENT'S SADISTIC BEHAVIOR OR BECAUSE OF THEIR ROLE AS OLDEST CHILD. THE SURVIVING PARENTS TENDED TO BE PASSIVE AND DEPENDENT. OFTEN THE RELATIONSHIP BETWEEN PARENTS WAS A SADO-MASOCHISTIC ONE, WHICH PREVENTED DISSOLUTION OF THE MARRIAGE OR CONTROL OF THE SADISTIC BEHAVIOR. CATASTROPHIC CONFLICTS AROSE WITHIN THE PERPETRATORS FROM THE DISTURBANCES IN FAMILY LIFE. SOCIETAL RESPONSES TO THE TROUBLED FAMILIES WERE INEFFECTIVE, IMPRESSING UPON THE PERPETRATORS A SENSE OF FUTILITY AND POWERLESSNESS. THE SLAYING OF THE PARENT LED TO A GENERAL IMPROVEMENT IN FAMILY LIFE, EVEN TO OPEN RELIEF AND REJOICING. THERE WAS A DISTINCT ABSENCE OF MOURNING AND GUILT ON THE PART OF THE PERPETRATOR AND OTHER MEMBERS OF THE FAMILY. THE DEGREE OF IMPROVEMENT IN FAMILY LIFE AFTER THE KILLING DEPENDED ON THE HANDLING OF THE CASE. THESE KILLINGS WERE COMMITTED BECAUSE THE ADOLESCENTS WERE SUFFICIENTLY AUTONOMOUS TO PLAN AND CARRY OUT THE KILLINGS, AND YET TOO DEPENDENT TO BREAK AWAY FROM PARENTAL TYRANNY. A BETTER UNDERSTANDING OF THE EVOLUTION OF REACTIVE PARRICIDE, WHICH IS A LAST RESORT TO PROTECT THE PSYCHIC INTEGRITY OF THE PERPETRATOR THREATENED WITH PSYCHIC DISINTEGRATION DUE TO CASTASTROPHIC CONFLICT, MAY LEAD TO MORE REALISTIC HANDLING OF THESE SITUATIONS AND TO THE PREVENTION OF THE MOST EXTREME CONSEQUENCE OF PARENTAL ABUSE. A LIST OF REFERENCES IS INCLUDED. (LKM)