OBJECTIVE - To evaluate the effectiveness of behavioral interventions for adolescents with type 1 diabetes based on a systematic review of the literature. RESEARCH DESIGN AND METHODS - The literature was identified by searching 11 electronic databases, hand-searching 3 journals from their start dates, and contacting individual researchers. Only articles that reported evaluations of behavioral (including educational and psychosocial) interventions for adolescents (age range 9-21 years) with type 1 diabetes that included a control group were included in the present review. Data summarizing the key features of the interventions and their effects were extracted from each article. Where possible, effect sizes for the randomized control trials (RCTs) were calculated. RESULTS - The search process identified 64 reports of empirical studies. Of these, 35 studies included a control group, and 24 were RCTs. Effect sizes could be calculated for 18 interventions. The overall mean effect size calculated across all outcomes was 0.33 (median 0.21), indicating that these interventions have a small- to medium-sized beneficial effect on diabetes management. Interventions that were theoretically based were significantly more effective than those that were not (P < 0.05, 1-tailed). CONCLUSIONS - Research to date indicates that these interventions are moderately effective. Several methodological weaknesses to be avoided in future studies are noted. It is also recommended that investigators use the reach, efficacy, adoption, implementation, and maintenance (RE-AIM) framework to guide the design of future studies, which should result in more disseminable interventions. RE-AIM assesses the intervention's reach, or percent or representativeness of patients willing to participate; efficacy across a range of outcomes; adoption, or the percent and representativeness of settings willing to implement the intervention; implementation, or the consistency of the delivery of the intervention as intended; and maintenance, or the extent to which delivery of the intervention becomes a routine part of health care in the medical setting.