THE HISTORICAL CONTEXT AND PROVISIONS OF CALIFORNIA'S MENTALLY DISORDERED SEX OFFENDER (MDSO) ACT ARE REVIEWED. APPLICATION OF THE MDSO LAW IN EVERYDAY PRACTICE IS DESCRIBED, WITH EMPHASIS ON SIMILARITIES AMONG CRIMINAL COURTS IN THREE COUNTIES. THE PROCESSES AND PARTICIPANTS INVOLVED IN DETERMINING THE TYPE OF SANCTION TO BE IMPOSED ON SEX OFFENDERS IN THE THREE COUNTIES ARE EXAMINED, WITH EMPHASIS ON DECISIONMAKERS (JUDGES, DISTRICT ATTORNEYS, DEFENSE ATTORNEYS) AND ASSISTANTS TO THE COURTS (PROBATION OFFICERS AND PSYCHIATRISTS). ISSUES RELATED TO ARBITRARY SENTENCING POLICY, DISCRETION IN SENTENCING, AND THE RELATIONSHIP BETWEEN THE COURTS AND THE HOSPITAL TO WHICH MDSO'S ARE COMMITTED ARE EXPLORED. IMPLICATIONS OF THE STUDY'S FINDINGS ARE DISCUSSED. IT IS CONCLUDED THAT A TREND TO CIVIL COMMITMENT IS LIKELY TO CONTINUE AND THAT IT IS CHARACTERISTICS OF THE TRADITIONAL CRIMINAL SANCTION, THAT THIS TREND TOWARD 'CRIMINALIZATION' OF CIVIL COMMITMENT IS OCCURRING THROUGHTOUT THE COUNTRY AND IS LIKELY TO CONTINUE, AND THAT THE TREND IS DESIRABLE. SUPPORTING DATA ON ADJUDICATION OF SEX OFFENSES IN THE THREE STUDY COUNTRIES ARE INCLUDED. (LKM)