BACKGROUND: Advice is widely considered an effective treatment for acute low back pain (LBP); however, details on what and how to deliver this intervention is less clear. PURPOSE: We assessed and compared clinical trials that test advice for acute LBP with practice guidelines for their completeness of reporting and concordance on the content, method of delivery, and treatment regimen of advice interventions. DESIGN/SETTING: Systematic review. METHODS: Advice randomized controlled trials were identified through a systematic search. Guidelines were taken from recent overviews of guidelines for LBP. Completeness of reporting was assessed using the Template for Intervention Description and Replication checklist. Thematic analysis was used to characterize advice interventions into topics across the aspects of content, method of delivery, and regimen. Concordance between clinical trials and guidelines was assessed by comparing the number of trials that found a statistically significant treatment effect for an intervention that included a specific advice topic with the number of guidelines recommending that topic. RESULTS: The median (interquartile range) completeness of reporting for clinical trials and guidelines was 8 (7-9) and 3 (2-4) out of nine items on the Template for Intervention Description and Replication checklist, respectively. Guideline recommendations were discordant with clinical trials for 50% of the advice topics identified. CONCLUSION: Completeness of reporting was less than ideal for randomized controlled trials and extremely poor for guidelines. The recommendations made in guidelines of advice for acute LBP were often not concordant with the results of clinical trials. Taken together, these findings mean that the potential clinical value of advice interventions for patients with acute LBP is probably not being realized.