The objective was to undertake a systematic review of the performance of wound measurement instruments used for patients with pressure ulcers. Studies of any design, evaluating methods for estimating wound diameter, depth, surface area, or volume in patients with pressure ulcers were included. Eligible evaluations had to report intra- or inter-rater reliability, accuracy, agreement, or feasibility of methods. Electronic databases and other sources were accessed for study identification. Included studies were critically appraised using a modified checklist for diagnostic test evaluations. Twelve studies were included. Most had methodological problems and/or used inappropriate statistical methods. Reliable methods for measuring pressure ulcer surface area may include: grid tracings from photographs combined with whole plus partial square count; a portable digital pad; and stereophotogrammetry combined with computerized image analysis. The agreement between photographic tracing and direct transparency tracing may be satisfactory (both methods being combined with computerized planimetry). No definitive conclusions could be reached about studies of diameter or depth; this means that there is little evidence to underpin recommendations in clinical guidelines. Evaluations of volume measurement were of poor quality, and there were few data on feasibility. Further primary research is needed to evaluate methods of wound measurement used in clinical practice.