This study had three goals: first, to investigate whether sexually explicit Internet material (SEIM) affects sexual risk behavior; second, to study whether these effects differ between adolescents and adults; and third, to analyze, separately for adolescents and adults, whether gender and age moderate an influence of SEIM on sexual risk behavior. The authors conducted a 2-wave panel survey among nationally representative random samples of 1,445 Dutch adolescents and 833 Dutch adults. SEIM use increased sexual risk behavior among adults, but not among adolescents. More specifically, moderator analyses showed that SEIM use increased sexual risk behavior only among male adults, but not among female adults. In the adolescent sample, no moderating gender effect occurred. Neither among adolescents nor among adults did age moderate the effects. Our study shows that SEIM may influence outcomes related to people's sexual health. It also suggests that male adults may present a potential risk group for adverse effects of SEIM.