While some Nigerian communities used prisons to segregate offenders from the general population, the modern concept of prison organization and administration was introduced by the British colonial administration. The present system still conforms to the British model. In 1981 there were 36,069 Nigerians, of which 98 percent were males, in 126 prisons. The prison population consists of people awaiting or undergoing trial, offenders convicted but not yet sentenced, and sentenced inmates. The typical inmate is a property offender, has an inadequate education and income, comes from a broken home, and is an anonymous stranger in the city. He is likely to be under 35 years old, married, and have many dependents. Imprisonment is a common sentence in Nigeria, and the prisons lack rehabilitation programs and educational facilities. Barriers to rehabilitating prisoners include appalling overcrowding, the infrequent use of bail to release offenders awaiting trial, a lack of psychiatric expertise, little classification of accommodations according to offense types, antiquated prison structures, and a serious shortage of experienced manpower. Other problems include insufficient financial support of the prison staff, no prerelease or postrelease programs, high staff turnover, difficulties in finding jobs for ex-offenders, and little cooperation among criminal justice agencies. In sum, Nigerian prisons must be cleared of people who should not be there and more adequate provision made for those who should go there. The paper contains 33 footnotes.