To access publisher's full text version of this article click on the hyperlink at the bottom of the pageTo systematically review the current literature on the effect of using ultrasound (US) guidance for the placement of peripheral intravenous (PIV) catheters in patients with difficult access.A systematic search was performed for the keywords ultrasonography, catheterization, and peripheral vein. A systematic review was performed on randomized-controlled studies comparing the use of dynamic US guidance with the conventional landmark technique. The primary outcome was the success rate of PIV placement and the secondary outcomes included the number of attempts and time to successful PIV placement.A total of 1778 titles were identified from the search and the review identified 50 potentially relevant studies that were reviewed comprehensively; six articles were included in the final review. The six studies enrolled a total of 316 patients, 153 in the control group and 163 in the US group. Two of the studies reported a significantly higher success rate for US on the basis of initial success or the overall success rate. The two pediatric studies found that time to successful cannulation was shorter and fewer attempts were required to achieve success for patients randomized to US compared with the traditional method. The six studies included were found to vary significantly in the definition of difficult venous access, recording of procedure time, definition of success rate, and other important factors, making a meta-analysis inappropriate.On the basis of this review, routine use of US guidance for PIV placement is not strongly supported by the literature