The objective of this article was twofold (1) to determine the existence and effectiveness of interventions to improve health professionals' management of obesity or the organization of care for overweight and obese people; and (2) to update a previous systematic review on this topic with new or additional studies. The study design was a systematic review of intervention studies, undertaken according to standard methods developed by the Cochrane Effective Practice and Organization of Care (EPOC) Group. Participants were trained health care professionals and overweight and obese patients. The measurements were objective measures of health professionals' practice and behaviours, and patient outcomes including satisfaction, behaviour, psychological factors, disease status, risk factors and measures of body weight, fat, or body mass index (BMI). Twelve studies were included in the original review. A further six were included in this update. Six of the 18 studies were randomized controlled trials of health professional-oriented interventions (such as the use of reminders and training) and one was a controlled before-and-after study to improve collaboration between a hospital clinic and general practitioners (GPs). Ten randomized controlled trials and two controlled clinical trials of interventions comparing either the deliverer of weight-loss interventions or the setting of the delivery of the intervention, were identified. The heterogeneity and generally limited quality of identified studies make it difficult to provide recommendations for improving health professionals' obesity management. To conclude, at present, there are few solid leads about improving obesity management, although reminder systems, brief training interventions, shared care, inpatient care and dietitian-led treatments may all be worth further investigation. Therefore, decisions for the improvement of provision of services must be based on the existing evidence on interventions with patients and good clinical judgement. Further research is needed to identify cost-effective strategies for improving the management of obesity. A full version of this review (including detailed descriptions of the included studies and their methodological quality, and results and excluded studies tables) is available in the Cochrane Library. The Cochrane Library is a database of systematic review and other evidence on the effects of health care, continuously updated as new information emerges. It is available on CD ROM from Update Software. For further information see: http://www.update-software.com/cochrane.