This study examined HIV knowledge, perceived risk and sexual behavior of 370 undergraduate students in selected universities in southern Nigeria. MANOVA confirmed females to have significantly higher overall HIV knowledge than males ([p.bar] = .03). In addition, more females than males reported significantly higher knowledge on the risk of HIV transmission through oral sex (p = .001). Females scored higher on the erroneous belief that antibiotics protect a person from HIV ([p.bar] = .008). Females showed greater knowledge on the risk of needle sharing in steroid use ([p.bar] = .001). but less knowledge on the erroneous assumption that women are tested for HIV during their pap smear assessments (p = .004). T-test on sexual behavior risk confirmed that males engage in more risky behaviors ([p.bar] =.002) than females. T-test showed a significant gender difference with males reporting greater overall susceptibility for HIV than females ([p.bar] = .009.