The SIR scale was developed as part of a the Parole Decision Making Project which examined factors that led to decisions made by the National Parole Board. The SIR Scale is a statistical model of significant factors that contribute to recidivism patterns in large groups of offenders; its validity has been reaffirmed by a Toronto research group. In addition research indicates that statistical methods, used with large numbers of cases, are more accurate than judgments of a cross-section of decision makers in predicting recidivism. Critics of the SIR Scale claim that the Scale is not based on Canadian offenders; that it is antiprofessional; that it does not apply to individuals; that it is past-oriented; and that it is not applicable to women, Native Americans, provincial offenders, or other subgroups. It also does not incorporate certain factors such as alcohol and is vulnerable to legal action. Supporters of the SIR counter-argue that numerous professionals rely on established diagnostic techniques in decision making processes, that no prediction instrument can tell with certainty whether a given offender will or will not recidivate, and that there has never been a successful legal challenge to the use of statistical aids in release decision making. In general, the SIR Scale can serve as an invaluable tool in professional decision making process and in effective correction interventions. 1 figure