BACKGROUND: Weight gain is commonly reported as a side effect of hormonal contraception and can lead to method discontinuation or reluctance to initiate the method. The purpose of this study was to investigate weight change in adolescent (aged 15-19 years) users of depot-medroxyprogesterone acetate (DMPA), norethisterone enanthate (NET-EN), combined oral contraceptives (COCs) and discontinuers of these methods as compared to nonusers of hormonal contraception. STUDY DESIGN: This longitudinal study recruited initiators of DMPA (n=115), NET-EN (n=115), COCs (n=116) and nonusers of contraception (n=144). Participants were followed up for 4-5 years, and details of current contraceptive method, including switching, discontinuing and/or starting hormonal methods were documented at each 6-monthly visit. Women were classified according to their contraceptive histories on completion of the study, and injectable users were combined into one group for analysis. Height, weight and self-reported dieting were recorded at each visit. RESULTS: There was no difference in mean age or weight between the groups at baseline. Women using DMPA or NET-EN throughout, or switching between the two, had gained an average of 6.2 kg compared to average increases of 2.3 kg in the COC group, 2.8 kg in nonusers and 2.8 kg among discontinued users of any method (p=.02). There was no evidence of a difference in weight gain between women classified as nonobese or classified as overweight/obese in any of the four study groups at baseline. CONCLUSION: There is fairly strong evidence that adolescent contraceptive hormonal injectable users appear to gain more weight than COC users, discontinuers and nonusers of contraception.