The dangerous sexual offender legislation (DSO) defined a DSO as a person who has shown a failure to control his sexual impulses, and who is likely to cause injury, pain or other evil to any person in the future. Data for this report were taken from an analysis of all the DSO case files maintained by the National Parole Board up to 1974. A further and more detailed examination, including psychiatric interventions and parole outcomes, was made of the clinical administrative records of all 34 of the British Columbia and 28 Ontario DSO's up to 1974. The data leave little doubt that in its 29 years of operation, the DSO legislation has failed to achieve its purposes. The Government did not fulfill its promise to provide effective treatment facilities and because 'dangerous sexual offender' is a political and legal category rather than a clinical diagnosis. Further, the courts, aided by psychiatrists, were incapable of distinguishing between offensive but relatively harmless pedophiles and dangerous habitual rapists. The most grievous failure has been that neither the parole board nor the psychiatrists and psycholgists serving the board have demonstrated a capacity to predict reliably the DSO's future capacity for dangerous behavior, as high rate of parole revocations (38 percent) indicates. Although the DSO legislation was repealed in 1977, many of those sentenced under the legislation are still imprisoned under the terms of the legislation. The Government has yet to pursue the recommendation of the Law Reform Commission that a judge be appointed to review these cases with a view toward establishing a release program and periodic case review. Fifteen references are provided.