Objective: The maxillary artery (MA) and its terminal branches are frequently damaged in the maxillary osteotomy, especially during separation of the pterygomaxillary junction (PMJ). The aims of this study were to evaluate the positional relationship between the MA at the pterygomaxillary fissure and the PMJ in Thais, as well as to measure the diameter of the MA as it enters the pterygopalatine fossa (PPF). Methods: With the lateral infratemporal approach, the branches from the third part of the MA, PMJ and posterolateral maxilla were dissected in 100 Thai adult cadavers. Measurements taken included the following: (1) the distance (in mm) from the most inferior point of the PMJ to the most inferior position of the MA as it entered the PPF; (2) the external diameter of the MA as it entered the PPF; (3) vertical heights of the PMJ, maxillary tuberosity and posterior maxilla. Results: The results showed that MA entered the PPF at a mean distance of 23.5±2.5 mm above the most inferior point of the PMJ. The mean external diameter of the MA as it entered the PPF was 2.8±0.6 mm. Mean heights of the PMJ, maxillary tuberosity, and posterior maxilla were 19.5±2.3 mm, 6.1±2.7 mm, and 25.6±3.3 mm, respectively. Conclusion: In conclusion, the mean location of the MA was 23.5 mm apart from the most inferior point of the PMJ, therefore, dysjunction of the PMJ using an osteotome with a 15-mm cutting edge may be conducted without damaging to the MA. This study was supported by a grant from the Dental Research Fund, Faculty of Dentistry, Chulalongkorn University, Thailand.