We investigated the sensitivity of our phallometric test for pedophilia (and hebephilia). An initial sample of subjects included 47 men accused of sexual offenses against minors and 26 control subjects-men accused of offenses against adult women (exhibitionism, rape, or sexually sadistic activity). A second sample included 107 offenders against minors and 30 control subjects. In both samples, the offenders against minors were further classified according to the targets of their sexual offenses (girls, boys, or both) and according to the extent to which they admitted an erotic preference for the immature physique. Computerized diagnostic rules were developed with the first sample and cross-validated with the second. The sensitivity of the test in detecting pedophilia or hebephilia in complete nonadmitters is probably greater than or equal to 55% but is certainly less than 100%. Its specificity appears to be over 95%.