Presently, there are no established scales that evaluate change in risk among sexual offenders. The Sex Offender Need Assessment Rating (SONAR) was developed to fill this gap. The SONAR includes five relatively stable factors (intimacy deficits, negative social influences, attitudes tolerant of sex offending, sexual self-regulation, general self-regulation) and four acute factors (substance abuse, negative mood, anger, victim access). The psychometric properties of the scale were examined using data previously collected by Hanson and Harris (1998, 2000). Overall, the scale showed adequate internal consistency and moderate ability to differentiate between recidivists and nonrecidivists (r = .43; ROC area of .74). SONAR continued to distinguish between the groups after controlling for well-established risk indicators, such as age, and scores on the Static-99 (Hanson & Thornton, 2000) and the Violence Risk Appraisal Guide (Quinsey, Harris, Rice, & Cormier, 1998).