BECAUSE THE RAPIDLY GROWING INMATE POPULATION IN GREAT BRITAIN IS OVERFLOWING EXISTING INSTITUTIONAL CAPACITY, NUMEROUS PROPOSALS HAVE BEEN MADE TO REDUCE IT. THIS STUDY GATHERS STATISTICS FROM THE 1975 'ANNUAL REPORT ON THE PRISON DEPARTMENT,' EXTRAPOLATES FROM THEM WHERE NECESSARY, AND ANALYZES THEM TO PROVIDE A BASIS FOR DECISIONMAKING. THE FIGURES SHOW THAT THE INCREASES HAVE NOT BEEN UNIFORM OVER ALL CATEGORIES. THE LARGEST HAVE HAVE BEEN IN CATEGORIES WHICH, UNDER PRESENT LAW, DETAINEES SHOULD NOT BE IN PRISON AT ALL; I.E., JUVENILES, REMAND PRISONERS AWAITING TRIAL OR SENTENCE, AND IMMIGRANTS. IT IS SUGGESTED THAT THE PRISON POPULATION CRISIS HAS BEEN LARGELY PRODUCED BY INCREASED INCARCERATION OF JUVENILES AND REMAND PRISONERS. THE REMAND CATEGORY HAS DOUBLED SINCE 1966. REMAND OF THOSE AGED 14 TO 16 HAS INCREASED BY ALMOST 60 PERCENT, WHILE THE GROUP OVER AGE 17 DECREASES MARGINALLY. MANY ARE EVENTUALLY FOUND NOT GUILTY OR RECEIVE NONCUSTODIAL SENTENCES. A SIMILAR ANALYSIS IS CONDUCTED FOR JUVENILE OFFENDERS. IT IS CONCLUDED THAT UP TO HALF THE DETENTION CENTER INMATES AND ABOUT 1 IN 6 OF THE BORSTAL INMATES HAVE BEEN CONVICTED OF MINOR OFFENSES. IT IS SUGGESTED THAT BOTH FORMS OF INCARCERATION ARE OVERUSED. TABLES ANALYZE CHARACTERISTICS OF ADULT PRISONERS, CIVIL PRISONERS, FINE DEFAULTERS, AND FEMALE OFFENDERS. IT IS SUGGESTED THAT BETTER PROCEDURES CAN BE DEVELOPED FOR THE HANDLING OF IMMIGRATION OFFENSES AND THAT WAGE ATTACHMENTS WOULD BE MORE EFFECTIVE AGAINST FINE DEFAULTERS. AN ANALYSIS OF DANGEROUSNESS OF DETAINED OFFENDERS CONCLUDES THAT IF ONLY THOSE POSING A THREAT TO SOCIETY WERE INCARCERATED, THE PRISON POPULATION COULD BE REDUCED FROM 1975'S AVERAGE OF 39,820 TO ABOUT 20,500. REFERENCES ARE INCLUDED. (GLR)