Outcomes from 42 studies of psychological interventions for children and adolescents with chronic medical conditions were analyzed using meta-analysis. Studies were divided into the four intervention categories suggested by LaGreca and Varni (1993), Disease Management, Emotional/Behavioral Problems, Health Promotion, and Prevention. Results supported overall effectiveness of psychological interventions, with an effect size (ES) of 1.12, as well as maintenance of treatment gains for at least 12 months posttreatment. Psychological interventions directed at disease-related or emotional/behavioral problems were both found to be effective, although too few studies of health promotion or disease prevention interventions were identified to be included in the analysis. Effectiveness of behavioral interventions, which were most heavily represented in the sample, demonstrated similar effects for disease management (ES = 1.20) and emotional/behavioral (ES = 1.03) problems. Although disease type, severity, and duration did not affect intervention effectiveness, some influences of patient age and gender were noted across studies. Recommendations for further intervention studies and improvements in study design are discussed.