Describes a research project undertaken to provide data on five basic questions regarding the assessment and prediction of criminal behaviour: which predictor domains can predict recidivism; whether dynamic predictors as a group are inferior to static predictors in their ability to predict recidivism; whether differences exist among composite measures of risk prediction instruments and measures of antisocial personality in their ability to predict recidivism; whether the most robust predictors of recidivism are associated with different theories of criminal behaviour; and which practical guidelines from this research can assist practitioners in making better assessments of criminal behaviour. The project used meta-analysis of the literature on adult recidivism prediction; 131 studies produced 1141 correlations with recidivism and the strongest predictor domains were identified. Recommendations for developing sound assessment practices in corrections are also provided.