BACKGROUND: A panel of experts convened by the American Dental Association Council on Scientific Affairs presents an evidence-based clinical practice guideline on nonsurgical treatment of patients with chronic periodontitis by means of scaling and root planing (SRP) with or without adjuncts. METHODS: The authors developed this clinical practice guideline according to the American Dental Association's evidence-based guideline development methodology. This guideline is founded on a systematic review of the evidence that included 72 research articles providing clinical attachment level data on trials of at least 6 months' duration and published in English through July 2014. The strength of each recommendation (strong, in favor, weak, expert opinion for, expert opinion against, and against) is based on an assessment of the level of certainty in the evidence for the treatment's benefit in combination with an assessment of the balance between the magnitude of the benefit and the potential for adverse effects. PRACTICAL IMPLICATIONS AND CONCLUSIONS: For patients with chronic periodontitis, SRP showed a moderate benefit, and the benefits were judged to outweigh potential adverse effects. The authors voted in favor of SRP as the initial nonsurgical treatment for chronic periodontitis. Although systemic subantimicrobial-dose doxycycline and systemic antimicrobials showed similar magnitudes of benefits as adjunctive therapies to SRP, they were recommended at different strengths (in favor for systemic subantimicrobial-dose doxycycline and weak for systemic antimicrobials) because of the higher potential for adverse effects with higher doses of antimicrobials. The strengths of 2 other recommendations are weak: chlorhexidine chips and photodynamic therapy with a diode laser. Recommendations for the other local antimicrobials (doxycycline hyclate gel and minocycline microspheres) were expert opinion for. Recommendations for the nonsurgical use of other lasers as SRP adjuncts were limited to expert opinion against because there was uncertainty regarding their clinical benefits and benefit-to-adverse effects balance. Note that expert opinion for does not imply endorsement but instead signifies that evidence is lacking and the level of certainty in the evidence is low.