Aim:Transoral and transnasal routes require information about bony and neurovascular structures. The aim of this study is to evaluate anatomical data of the bony structures, seen during anterior exploration of the C1-C2 complex. Material and Methods:This study was performed on six formalin fixed cadaveric head, neck specimens. The study included radiological, anatomical measurements. The distances between C1-C2, bony distance between C1 anterior tubercle - the superior dentes incisivus, height of the C1 anterior arch, width and height of odontoid articular surface were measured.Results:The mean distance between C1 anterior tubercle-nares and superior incisors on maxilla, were measured as 96.16±8.07 mm, and 84.14±9.16 mm, respectively. The mean height of C1 anterior arch was 13.89 mm. The mean distance between medial borders of right-left C1 lateral masses was found to be 19.10±1.80 mm. The mean distance between medial border of lateral mass-midline in right, left sides were found to be 9.43±0.88 and 9.68±0.97 mm respectively. The mean height of C1 anterior arch at midline was mesaured as 13.892.48 mm, and the mean distance between ventral surface of anterior arch and ventral joint of odontoid on ML was found to be 6.43±1.29 mm. The anteroposterior, horizontal diameters of odontoid on its base were measured as 12.12±0.38 mm, and 11.12±0.94 mm, respectively. The angle of transoral, transnasal approach to C1 were found to be 32.67±4.59 degree and 32.00±2.10 degree respectively.Conclusion:A safe transoral odontoidectomy requires knowledge regarding ventral C1-C2 relationships, regarding distances of odontoid, lateral mass, midline.