This study investigated whether the previously observed association of pedophilia with lower IQs is an artifact of heterogeneity in referral source. The subjects were 832 adult male patients referred to a specialty clinic for evaluation of their sexual behavior. The patients' erotic preferences for prepubescent, pubescent, or adult partners were assessed with phallometric testing. Full scale IQ was estimated using six subtests from the WAIS-R. The results showed that the relations between pedophilia and lower IQ, lesser education, and increased rates of non-right-handedness were the same in homogeneous groups referred by lawyers or parole and probation officers as they were in a heterogeneous group referred by a miscellany of other sources. Those results, along with secondary analyses in the study, supported the conclusion that the relation between pedophilia and cognitive function is genuine and not artifactual. The findings were interpreted as evidence for the hypothesis that neurodevelopmental perturbations increase the risk of pedophilia in males.