The study's purpose was to determine which factors were the strongest predictors of tobacco smoking behaviors among U.S. adolescents. The population included a nationally representative sample of 6,504 adolescents residing in the U.S. Data were collected in respondents 'homes using trained interviewers. Weighted population estimates showed that over half (55.6%) of adolescents had "ever tried smoking," nearly half of whom (48.2%) reported "regular smoking." Those whose closest friends smoked were twice as likely to "ever smoke " (OR = 2.24, p<.001), twice as likely to be a "regular smoker" (OK = 2.28, p <.OO1), and more likely (b = 5.15p <.OO1) to have smoked daily than those whose friends do not smoke. Results show the very strong influence of friendships on tobacco initiation and continuance among this national sample of adolescents. Recommendations for primary and secondary prevention are noted.