Detailed research examining concurrent longitudinal and secular changes in adolescent beverage intake is not currently available, particularly since the year 2000. This study's objective was to evaluate these trends in beverage intake in a large, diverse adolescent cohort. Project EAT (Eating Among Teens)-II is a 5-year longitudinal study (n=2,516) including two cohorts, which allows for the observation of longitudinal changes from early to mid-adolescence (junior high to high school) and from mid- to late adolescence (high school to post high school). Project EAT-II also examined secular trends in adolescent health behavior from 1999-2004 in mid-adolescence. Daily beverage servings were assessed using the Youth and Adolescent Food Frequency Questionnaire. Longitudinal findings indicate that intake of soda and sugar-sweetened beverages (including soda, sweetened iced teas, and fruit drinks) increased significantly among younger males, and alcohol increased across all groups (P<0.01). Consumption of certain beverages decreased with age: fruit juice (among all males and older females, P< or =0.02), milk (older adolescents, P<0.01), other milk beverages (all females and older males, P<0.01), diet soda (younger adolescents, P<0.01), and coffee/tea (all males and younger females, P<0.01). Significant secular decreases were observed in fruit juice and coffee/tea for males and females (P< or =0.05). Overall, these findings reflect recent secular and longitudinal shifts in adolescent beverage consumption during the critical transition period from early to mid-adolescence and mid- to late adolescence. Although additional research is needed to better understand nuances in adolescent consumption patterns, registered dietitians and other health care practitioners working with adolescents should address the importance of limiting sugar-sweetened beverages with low nutrient density.