The main elements of modern parole can be traced back to a variety of sources, including "good-time" laws, tickets-of-leave, executive pardons, and compulsory aftercare. Parole emerged at different times and in response to different pressures in the United States, Canada, and England and Wales. In the 1970's the entire penal system of rehabilitation, indeterminate sentencing, and parole came under attack for its alleged ineffectiveness, uncontrolled discretion, and denial of due process. In the United States, many States abolished parole and introduced determinate sentencing; others developed parole or sentencing guidelines. In England, the pressures of prison crowding led to a rapid expansion of parole release, but at some compromise of its original principles and the independence of the parole board. Canada sought a new focus for parole decisions and introduced mandatory supervision for prisoners denied parole. In all three countries, the roles and purposes of parole release and postrelease supervision remain in controversy. 3 tables, 115 references. (Author abstract modified)