The original impetus for legislation grew out of the prospects for release of an accumulation of about 175 mentally ill prisoners who had already served an average of almost 4 years more than the applicable determinate sentences provided under California's retroactive Determinate Sentence Act of 1977. The accumulated prisoners were those having the most serious mental disorders of the approximately 5,500 prisoners slated for release in the 6 months following the effective date of the determinate sentence act. This group of disturbed prisoners, however, did no worse than the average paroles in terms of arrest frequency and appears to have done better with respect to return to prison. While by no means conducted as a scientific experiment, and with only limited followup data available, the experience clearly indicates the need for a formal period of parole supervision for this type of release. Despite the fact that some of those under supervision committed serious offenses, the parole system demonstrated that with the necessary resources it can control a particularly difficult, troublesome type of offender, and afford the public substantial protection that it would not otherwise have. Meanwhile, legislative research continues, and solutions proposed by some are rejected by others for their expense, their sketchiness, their restrictiveness in definitions of mentally diseased violent offenders, or their equation of mental illness with violence, when many persons who are violent are not mentally ill or vice versa. Nevertheless, the parole board has displayed remarkable capabilities for dealing with this kind of releasee, and the legislative search continues. (Author abstract modified)