OBJECTIVES: To obtain national estimates of youth involved in sexting in the past year (the transmission via cell phone, the Internet, and other electronic media of sexual images), as well as provide details of the youth involved and the nature of the sexual images. METHODS: The study was based on a cross-sectional national telephone survey of 1560 youth Internet users, ages 10 through 17. RESULTS: Estimates varied considerably depending on the nature of the images or videos and the role of the youth involved. Two and one-half percent of youth had appeared in or created nude or nearly nude pictures or videos. However, this percentage is reduced to 1.0% when the definition is restricted to only include images that were sexually explicit (ie, showed naked breasts, genitals, or bottoms). Of the youth who participated in the survey, 7.1% said they had received nude or nearly nude images of others; 5.9% of youth reported receiving sexually explicit images. Few youth distributed these images. CONCLUSIONS: Because policy debates on youth sexting behavior focus on concerns about the production and possession of illegal child pornography, it is important to have research that collects details about the nature of the sexual images rather than using ambiguous screening questions without follow-ups. The rate of youth exposure to sexting highlights a need to provide them with information about legal consequences of sexting and advice about what to do if they receive a sexting image. However, the data suggest that appearing in, creating, or receiving sexual images is far from being a normative behavior for youth.