. Two-year Internet-based randomized controlled trial for weight loss in African-American girls. Obesity. 2006;14:1231-1243. Objective: A randomized controlled trial tested the efficacy of an internet-based lifestyle behavior modification program for African-American girls over a 2-year period of intervention. Research Methods and Procedures: Fifty-seven overweight (mean BMI percentile, 98.3) African-American girls (mean age, 13.2 years) were randomly assigned to an interactive behavioral internet program or an internet health education program, the control condition. Overweight parents were also participants in the study. Forty adolescentparent dyads (70%) completed the 2-year trial. Outcome data including BMI, body weight, body composition, and weight loss behaviors were collected at baseline and at 6-month intervals. A computer server tracked use of the web sites. Results: An intention-to-treat statistical approach was used, with the last observation carried forward. In comparison with the control condition, adolescents in the behavioral program lost more mean body fat (BF) (Ϫ1.12 Ϯ 0.47% vs. 0.43 Ϯ 0.47% BF, p Ͻ 0.05), and parents in the behavioral program lost significantly more mean body weight (Ϫ2.43 Ϯ 0.66 vs. Ϫ0.35 Ϯ 0.64 kg, p Ͻ 0.05) during the first 6 months. This weight loss was regained over the next 18 months. After 2 years, differences in fat for adolescents (Ϫ0.08 Ϯ 0.71% vs. 0.84 Ϯ 0.72% BF) and weight for parents (Ϫ1.1 Ϯ 0.91 vs. Ϫ0.60 Ϯ 0.89 kg) did not differ between the behavioral and control programs. Discussion: An internet-based weight management program for African-American adolescent girls and their parents resulted in weight loss during the first 6 months but did not yield long-term loss due to reduced use of the web site over time.