THE OPERATIONS WERE PERFORMED AT THE REQUEST AND ON THE INITIATIVE OF THE FOUR DELINQUENT INMATES IMPRISONED FOR HETEROSEXUAL RAPES AND SEXUALLY MOTIVATED ARSON; SURGICAL CASTRATION HAD BEEN RECOMMENDED FOR TWO OF THE FOUR. LESIONS WERE PERFORMED BY AN ISOLATED WIRE ELECTRODE BELONGING TO THE STEREOTACTIC DEVICE OF REICHERT AND MUNDINGER. CASE HISTORIES ON EACH OF THE SUBJECTS DESCRIBE THEIR CRIMINAL BACKGROUNDS, THEIR OPERATIONS, AND THEIR POSTOPERATIVE COURSE. POSTOPERATIVE OBSERVATIONS AND EXAMINATIONS OF THE PATIENTS INDICATE A MARKED REDUCTION OF THEIR SEXUAL DRIVE; THIS REDUCTION WAS CONSIDERED TO BE AN IMPROVED ADAPTATION IN THEIR FORMERLY DISTURBED SPHERE. ALL FOUR OFFENDERS WERE RELEASED FROM JAIL BY JUDGES AS A RESULT OF THE OPERATIONS, AND NOT ONE OF THEM HAS RECIDIVATED. THE NUMBER OF POSTOPERATIVE SIDE EFFECTS WAS LOW--TWO PATIENTS EXPERIENCED STRONG HUNGER FEELINGS FOR 2 YEARS FOLLOWING THE OPERATION. DATA ARE STILL NOT AVAILABLE REGARDING THE SUFFICIENCY AND PERMANENCY OF THE REDUCTION OF SEXUAL DRIVE AND ITS LONG-TERM EFFECT ON SEXUALLY VIOLENT CRIMINALS. STUDY DATA, X-RAY PHOTOGRAPHS, AND REFERENCES ARE PROVIDED. (DAG)