The analysis reveals that the number of mentally ill offenders is much lower than has sometimes been assumed, but the complexity and apparent intractability of their needs make the aim of diversion alone an inadequate one. The likelihood that these offenders will continue to go to prison points to the urgent need to consider how a humane and therapeutic psychiatric service might be provided within the prison system. Moreover, diversion, if considered in terms of services located at individual entry points such as police stations or courts, is logistically extremely difficult. Court-based psychiatrists are clearly useful for the very small number who need immediate access to a hospital bed. For less acute cases, psychiatric assessment alone does little if unaccompanied by effective followup to community resources. Thus, a combination of access to specialized advice and assessment services, coupled with general awareness at all levels decisionmaking, is needed. Issues requiring particular attention are homelessness, drug abuse, personal violence, and race and ethnicity. Tables, notes, and 64 references