The azygos system veins vary greatly in their mode of origin, course, tributaries, anastomoses and termination. Therefore, we aimed to investigate the types of azygos system in this study. Our research was made in Anatomy departments on 48 conserved cadavers aging between 27-70 years, of which 35 were males and 13 females. In the research, the diameters and levels of the azygos vein, the hemiazygos vein, the accessory hemiazygos vein and the superior intercostal vein were investigated. The subjects were classified in Anson's system with a basis of vertical and horizontal connections in the azygos venous system the classification included primitive or embryological types, transient type, unicolon type as three basic types and their eleven subgroups. According to this classification (amongst 48 cadavers), one (2.1%) of our subjects was found to be Type I, 44 (91.7%) of them were found to be Type II, and one (2.1%) was found to be Type III. These values were similar to those in the literature, however two (4.2%) subjects did not fit in any otherwise defined groups and were named as atypic group. It is very important to identify the variations of the azygos system in the computed tomography and magnetic resonance imaging of mediastinum. The abnormal azygos venous system may easily be confused with aneurysm, lymphadenopathy and other abnormalities like tumor. It is important to keep these kinds of variations in mind while performing the mediastinal operations or surgery of large vessels.