Adolescents are frequently admonished to be socially assertive in order to confront negative interpersonal peer influences. Since the advent of HIV/AIDS in human social chemistry, the admonition has become more critical than ever. But the warning is often proffered in the misguided presumption that social assertiveness is the all-required psycho-structure against risk. The present cross-national study examines social and sexual assertiveness in four-country adolescent samples of Nigerian, Thai, Chinese, and Japanese college students. The findings reveal that sexual rather than social assertiveness was the sine qua non against risk, cross-culturally.