Objectives: Surgical removal of third molars is a regular surgical procedure, which like all operations, may have complications. The purpose of the study was to analyze the incidence of complications and their relationship with the surgical difficulty in a group of 588 patients treated by the same oral and maxillofacial surgeon. Study design: This retrospective cohort study consisted of 1699 third molars (M3) removed between 2005 and 2008. The teeth were grouped into a 6-class scale of surgical difficulty rated according to the surgical procedure description in the patient?s file: I: upper M3 requiring forceps only; II: upper M3 requiring osteotomy; III: upper M3 requiring osteotomy and tooth section; IV: lower M3 requiring forceps only; V: lower M3 requiring osteotomy; VI: lower M3 requiring osteotomy and tooth section. The complications were grouped into each surgical difficulty class and their incidence and management were also described. Results: 59 complications (3.47%), including pain, root tip fracture, paresthesia, alveolar osteitis, temporomandibular joint discomfort, and oroantral fistula were reported. Surgical difficulty class VI presented the higher incidence of complications (n=38). Conclusions: The risk of complications in third molar surgery will always exist and increases in proportion to the surgical difficulty. Mandibular M3 requiring osteotomy and tooth section have the highest risk of complications.