The purpose of this study was to perform a systematic review and meta-analysis of controlled trials to determine the effect of strength-training programs on the running economy (RE) of high-level middle- and long-distance runners. Four electronic databases were searched in September 2015 (Pubmed, SPORTDiscus, MEDLINE and CINAHL) for original research articles. After analyzing 699 resultant original articles, studies were included if the following criteria were met: (a) participants were competitive middle- and/or long-distance runners; (b) participants had a VO2max > 60mL[middle dot]kg-1-[middle dot]min-1; (c) studies were controlled trials published in peer-reviewed journals; (d) studies analyzed the effects of strength-training programs with a duration greater than 4 weeks; (e) RE was measured before and after the strength-training intervention. Five studies met the inclusion criteria, resulting in a total sample size of 93 competitive, high-level middle- and long-distance runners. Four out of five of the included studies used low to moderate training intensities (40-70% one-repetition maximum), and all of them used low to moderate training volume (2-4 resistance lower-body exercises plus up to 200 jumps and 5-10 short sprints) 2-3 per week for 8-12 weeks. The meta-analyzed effect of strength training programs on RE in high-level middle- and long- distance runners showed a large, beneficial effect (standardized mean difference [95%Confidence Interval] = -1.42 [-2.23, -0.60]). In conclusion, a strength-training program including low to high intensity resistance exercises and plyometric exercises performed 2-3 times per week for 8-12 weeks is an appropriate strategy to improve RE in highly training middle- and long-distance runners. Copyright (C) 2015 by the National Strength & Conditioning Association.