Describes trends in the composition of offenders under Federal probation, parole, or supervised release between 1987 and 1996. Between midyear 1987 and midyear 1996, the number of offenders under active supervision increased 21%, from 71,361 to 89,332. The number of offenders under probation supervision decreased 37% and the number under postimprisonment supervision (parole and supervised release) tripled. The proportion of defendants sentenced to imprisonment increased from 53% in 1987 to 69% in 1996.