The predictive validity of 2 risk assessment instruments for sex offenders, modified versions of the Static-99 and the Sex Offender Risk Appraisal Guide, was examined and compared in a sample of 258 adult male sex offenders. In addition, the independent contributions to the prediction of recidivism made by each instrument and by various phallometric indices were explored. Both instruments demonstrated moderate levels of predictive accuracy for sexual and violent (including sexual) recidivism. They were not significantly different in terms of their predictive accuracy for sexual or violent recidivism, nor did they contribute independently to the prediction of sexual or violent recidivism. Of the phallometric indices examined, only the pedophile index added significantly to the prediction of sexual recidivism, but not violent recidivism, above the Static-99 alone.