In the second of these four chapters on risk assessment, we discuss the empirical development and evaluation of actuarial risk assessment instruments (ARAIs). First, we describe the empirical development and evaluation of a brief actuarial scale (BAS). Second, we discuss how evaluation of predictive accuracy of ARAIs is accomplished using receiver operating characteristic (ROC) analysis. Third, we review the most popular and most often used ARAIs, and examine the empirical data supporting their use, particularly independent cross-validation studies. Fourth, we discuss the effects of aging on sex offender recidivism risk and the recent development of the static instruments which have incorporated a revised age item. Finally, we summarize the state of the art of sex offender risk prediction as of the end of the year 2012.