Using retrospective self-reporting, rates of illegal and legal performance-enhancing substance (PES) use in the past three months among more than 3,400 Italian high school adolescents were obtained and estimated. The study focused on the extent to which these sociodemographic characteristics and illegal PES use were associated with adolescents' positive attitudes toward illegal PES use. Results showed that it is relatively rare for youths to report use of illegal performance-enhancing substances in the past three months, and that male, relatively older, and athlete students were significantly more likely to use illegal PES than their respective counterparts. The results also showed that illegal PES users and male, older, and athlete students held stronger attitudes favoring illegal PES use. Finally, results showed that those student athletes who reported having used legal PES in the past three months were 10 times more likely to also have used illegal PES than those student athletes who did not report having used legal PES. (Contains 4 tables and 1 note.)