Aim. To highlight and discuss the practical aspects of conducting high quality, randomised controlled trials (RCTs) with overweight and obese children and their families. Content. Realistic considerations and suggestions for researchers arising from the experiences of three Australian interventions in overweight/obese children are highlighted. The practical implications of key issues arising during this type of RCT include study design, obtaining ethical approval, choice of outcome measures, recruitment, working with families, impact and process evaluation, retention strategies, managing multi-site trials and data management. Conclusion. Interventions for overweight children and their families are challenging. Although there were some differences in the design and outcome measures among the three studies, there were many similarities. Multi-site trials, although more expensive than single-site trials, are advantageous in increasing sample size and external validity. Collectively we have developed strategies to address key problems in conducting RCTs, including the common challenges of recruitment, retention and working with families.