Factors Associated With High-Quality Guidelines for the Pharmacologic Management of Chronic Diseases in Primary Care: A Systematic Review. Importance:  As the rate of publication of new and sometimes conflicting medical research increases, clinicians rely heavily on clinical practice guidelines (CPGs) to inform practice. However, CPGs are of widely variable quality, and there are no existing objective measures to rate the quality of CPGs. Objective:  To systematically assess 421 CPGs for the management of common noncommunicable diseases in primary care using the validated Appraisal of Guidelines for Research and Evaluation Instrument, version II (AGREE-II) tool and elucidate the factors associated with quality of CPGs. Evidence Review:  MEDLINE, Embase, the Cochrane Library, and 12 websites for CPGs were searched for CPGs for the management of common noncommunicable diseases in primary care published between January 1, 2011, and August 30, 2017. The assessment of the quality of CPGs was performed by 3 appraisers using the 6 domains of the AGREE-II instrument. A multiple logistic regression was performed to identify factors associated with quality of CPGs. Findings:  Of the 421 CPGs reviewed, 23.5% (99) were classified as high quality. Among included guidelines, clarity of presentation (70%) and scope and purpose (61%) had the highest median AGREE-II scores. The domains with the lowest median scores were applicability (22%) and rigor of development (33%). Factors associated with high-quality CPGs included having more than 20 authors (odds ratio, 9.08; 95% CI, 3.35-24.62), development at governmental institutions (odds ratio, 10.38; 95% CI, 2.72-39.60), and reporting funding (odds ratio, 10.34; 95% CI, 4.77-22.39). Year of publication, region, guideline version, and scope were not associated with quality among included CPGs. Conclusions and Relevance:  Primary care professionals and policymakers should be aware that CPGs in primary care are of widely variable quality, with less than 25% of included CPGs rated as high quality. High-quality CPGs were associated with a higher number of authors, governmental institutions, and the report of funding. Region of origin was not associated with quality of CPGs, which suggests that the improvement of the quality of CPGs should be an international concern.