The primary goal of nonsurgical periodontal therapy is to control microbial periodontal infection by removing bacterial biofilm, calculus, and toxins from periodontally involved root surfaces. A review of the scientific literature indicates that mechanical nonsurgical periodontal treatment predictably reduces the levels of inflammation and probing pocket depths, increases the clinical attachment level and results in an apical shift of the gingival margin. Another parameter to be considered, in spite of the lack of scientific evidence, is the reduction in the degree of tooth mobility, as clinically experienced. It is important to point out that nonsurgical periodontal treatment presents limitations such as the long-term maintainability of deep periodontal pockets, the risk of disease recurrence, and the skill of the operator. A high number of posttreatment residual pockets exhibiting bleeding on probing and > 5 mm deep are related to lower clinical stability. The successful treatment of plaque-induced periodontitis will restore periodontal health, but with reduced periodontium. In such cases, anatomical damage from previous periodontal disease will persist and inverse architecture of soft tissue may impair home plaque removal. The clinician can select one of the following therapeutic options according to the individual patient's needs: - Quadrant/sextant wise instrumentation (conventional staged debridement, CSD). - Instrumentation of all pockets within a 24-hour period with (full mouth disinfection [FMD]) or without (full mouth scaling and root planing [FMSRP]) local antiseptics. Both procedures can be associated with systemic antimicrobials. -CSD or FMD in combination with laser or photodynamic therapy. Patients with aggressive periodontitis constitute a challenge to the clinician. To date there are no established protocols for controlling the disease. However, data from the literature on the application of the FMD protocol combined with amoxicillin-metronidazole systemic administration are promising. A new classification in supra- and subcrestal nonsurgical periodontal therapy will be proposed. The supracrestal therapy includes the treatment of gingivitis, nonsurgical coverage of recession-type defects, treatment of suprabony defects and papilla reconstruction techniques. Within subcrestal periodontal therapy, it is of paramount importance to preserve both marginal tissues and connective fibers inserted in the root cementum at the apical part of the bony defects.