The author has observed the orthopantomograms of the maxillary sinus which were taken by special exposure method to study mesiodistal dimension, shape, symmetrical relationship, bony septum of the maxillary sinus and relationship between upper. 1st molar and the maxillary sinus, that were selected 56 cases of 23 to 27 years old male, who have good. systemic conditions and no missing teeth on upper posterior molar in normal occlusion, and obtained following conclusions: 1. Mesiodistal dimensions of the maxillary sinus are shown as follows; The mean of left dimension is 50.94±8.34㎜ and of right dimension is 49.50±9.87㎜. 2. To the shape of the maxillary sinus, V or U shape are 33cases(29.5%) and W shape are 77 cases(70.5%). 3. In the ralationship between upper 1st molar and floor of the maxllary sinus, superimposition are 62 cases (55.36%) and aproach are 50 cases (44.64%). 4. In the right and left symmetrical relationship of the maxillary sinus, symmetry are 37cases (66.07%) and asymmetry are 19 cases (33.93%). 5. The bony septums in the maxillary sinuses revealed that presence of bony septums are 29 cases (25.8%) and absence are 83 cases (74.11%).