Introduction: Everyday, the third molar's surgery is more frequent. That fact makes necessary to know the factors that allow to anticipate the surgical time and its characteristics. The aim of this research was to know the pre-surgical and surgical factors associated with the increase of the surgical time (IST) of the mandibular third molar (3M)'s surgery. Methodology: 145 subjects between the 15 - 40 years-old were selected from three surgical centers of Temuco (Chile). In this enclousures 158 surgeries were realized. All of the patients consulted by a 3M' s surgery, being put under surgical extraction in this centers. Variables from the patients, tooth and surgery itself were studied. The information were analyzed in the Stata 9.1 statistical package, utilizing the Fisher Test and Chi-Square Test, with p<0,05 for statistical significance. Results: The surgical time used in the surgery was minor of 20 minutes in the 50% of the cases and minor of de 30 minutes in the 75 % of the cases. The patient's age, the molar's position, the presence of pericoronaritis and the 3M' s root anatomy were significantly associated with a IST (p<0,05), of equal way the flap elevation, osteotomy and coronal or root section had statistical significance with IST (p<0,05). Conclusion: Factors like the patient's age, molar's position, surgeon's experience, pericoronaritis and the root fussion contribute significantly to and IST.