A retrospective longitudinal study was carried out to evaluate the efficacy of surgical and nonsurgical periodontal therapy in reducing pocket depth values. This evaluation was made in relation to the strictness with which patients observed professional and domestic oral hygiene and in relation to pretreatment pocket depth values. Results showed that the two forms of periodontal therapy offer comparable results in terms of pockets reduction of either restricted or considerable depth, whereas the most important element in order to achieve therapeutic success was the observation of an effective professional and domestic plaque control.