Up to a third of people with type 1 or 2 diabetes will develop microalbuminuria or macroalbuminuria after 20 years.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments in people with type 1 diabetes and early nephropathy? What are the effects of treatments in people with type 1 diabetes and late nephropathy? What are the effects of treatments in people with type 2 diabetes and early nephropathy? What are the effects of treatments in people with type 2 diabetes and late nephropathy? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2008 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 15 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review we present information relating to the effectiveness and safety of the following interventions: angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, captopril, glycaemic control, protein restriction, and tight control of blood pressure.