Self-sexualization refers to intentionally engaging in activities expressly to appear more sexually appealing. The purpose of our studies was to examine gender similarities and differences in how women and men conceptualize self-sexualization as well as introduce measures appropriate for large-scale data collection. In a qualitative study, we first established the existence of self-sexualization among women, although we were unable to document a similar construct among men. The Self-Sexualization Behavior Questionnaire for Women (SSBQ–W), developed over the course of three studies using samples from two small liberal arts colleges, demonstrated adequate internal consistency, stability, and construct validity. Discriminant validity for the SSBQ–W was demonstrated with the Surveillance subscale of the Objectified Body Consciousness Scale, the Sexualizing Behavior Scale, and the Enjoyment of Sexualization Scale. The SSBQ–W may especially be useful in addressing debates about the relationship of self-sexualization to sexual empowerment, agency, and oppression in young women. Additionally, our attempts to develop a parallel sound measure for men failed, and gender differences in item-by-item comparisons concluded that men are less likely to engage in specific self-sexualizing behaviors than women. These findings raise the possibility that self-sexualization is neither as meaningful nor as pervasive for men. In sum, our findings help to further refine how researchers and practitioners might best conceptualize self-sexualization, concluding that it is highly gendered activity that is largely confined to women and offering a measure for women that may promote further research.