Objective: To estimate the clinical and cost effectiveness of compression systems for treating venous leg ulcers. Methods: Systematic review of research. Search of 19 electronic databases including Medline, CINAHL, and Embase. Relevant journals and conference proceedings were hand searched and experts were consulted. Main outcome measures: Rate of healing and proportion of ulcers healed within a time period. Study selection: Randomised controlled trials, published or unpublished, with no restriction on date or language, that evaluated compression as a treatment for venous leg ulcers. Results: 24 randomised controlled trials were included in the review. The research evidence was quite weak: many trials had inadequate sample size and generally poor methodology. Compression seems to increase healing rates. Various high compression regimens are more effective than low compression. Few trials have compared the effectiveness of different high compression systems. Conclusions: Compression systems improve the healing of venous leg ulcers and should be used routinely in uncomplicated venous ulcers. Insufficient reliable evidence exists to indicate which system is the most effective. More good quality randomised controlled trials in association with economic evaluations are needed, to ascertain the most cost effective system for treating venous leg ulcers. Compression treatment increases the healing of ulcers compared with no compression High compression is more effective than low compression but should only be used in the absence of significant arterial disease No clear differences in the effectiveness of different types of compression systems (multilayer and short stretch bandages and Unna's boot) have been shown Intermittent pneumatic compression appears to be a useful adjunct to bandaging Rather than advocate one particular system, the increased use of any correctly applied high compression treatment should be promoted