The periodontal ligament tissue plays a crucial role in oral functions by providing structural support to the tooth. Due to the presence of undifferentiated mesenchymal cells, research into its regenerative capacity is ongoing. Pathological conditions can affect these functions and protein composition. The aim of this study was to evaluate through proteomic analysis the protein profile of the periodontal ligament (PDL) tissues of rats submitted to experimental periodontitis induction. The study was approved by the Ethical Committee on Animal Experimentation of the Sao Paulo State University, School of Dentistry at Araraquara, Brazil (protocol number 16/2015) and followed the Animal Research: Reporting of In Vivo Experiments guidelines. A total of eight male adult Holtzman rats, average weight of 300 g, were used and housed in plastic cages properly identified, with a 12-hours lights/dark cycle, under controlled temperature (22-25 °C), receiving water ad libitum and standard laboratory diet (Labina/Purina, Ribeirão Preto, Brazil). The animals were randomly assigned into two groups: control without any intervention (C, n=3) and experimental periodontitis (P, n=5). The animals of the group P were anesthetized with intramuscular injections of 10% ketamine chlorhydrate (0.08 ml/100 g body weight) and 2% xylazine chlorhydrate (0.04 ml/100 g body weight). To induce periodontitis, a cotton thread was placed bilaterally around the upper first molars and maintained with a knot for 20 days. After this period, all animals were euthanized by anesthetic overdose and had their maxillary jaws collected for subsequent analyses.