Five groups of males were compared on penile volume changes elicited from viewing short movie strips and slides of nude children and adults of both genders. Subject groups were sex offenders against adult females, volunteer controls who erotically preferred adult females, volunteer controls who erotically preferred adult males, heterosexual pedophiles, and homosexual pedophiles. Pedophiles differentiated erotically between females and males less than males who erotically preferred physically mature partners.