A central feature of Japanese corrections is the limited reliance on imprisonment, but despite the general trend of fewer and fewer convicted criminals entering prisons, at least six kinds of inmates ("cohorts") have assumed greater numbers in recent decades: offenders among the yakuza (members of crime syndicates), women drug offenders, traffic offenders, juvenile drug abusers and traffic offenders, offenders among foreigners (aliens convicted in Japan), and elderly offenders. In recent years, however, four of the six cohorts have abandoned their deviation from the general decline in imprisonment and also begun to decline; these groups are the yakuza, adult traffic offenders, women drug offenders, and juvenile traffic and drug offenders. The author's approach to explaining corrections trends in Japan is based on five premises. One premise is that prisons and community-oriented programs depend on society as a whole for the kinds and numbers of convicted offenders who come to them. The second premise is that the surge in the imprisonment of any group is due to the sudden appearance of a negative evaluation of that group's behavior. A third premise is that to understand criminological phenomena, one must understand the history, cultural beliefs, social psychology, and institutional environment of the people. A fourth premise is that operations of correctional agencies are worth scientific examination; and the fifth premise is that the annual statistics on correctional activities published by the Ministry of Justice are remarkable in world penology for their completeness. 45 tables, 280 references, and a subject index