The adult congenital hip dislocations and dysplasias have been previously classified by Eftekhar, Crowe et al., Hartofilakidis et al., Kerboul et al. and Mendes et al. The most conventient and widely used one is the Hartofilakidis and Crowe classification. Three different types of congenital hip disease in adults have been distinguished by Hartofilakidis and et al. based upon the position of the femoral head relative to the acetabulum: dysplasia; low dislocation; and high dislocation. All these classification systems are only radiological and does not highlight the operative technique in detail and the complications that we can observe perioperatively. Our classification system is also a radiological classification system but more useful for predicting the difficulty of the operative procedure and selecting the right operative method. In our classification system; at type I; dysplasia and less than 25% subluxations, we divided type I in to three subgroups, at type Ia, only dysplastic acetabulums, at type Ib, with elephant’s trunk type osteophyte formation and at type Ic, curtain type osteophytic formations, we included dysplasia and less than 25% subluxations in the same group because of operative technique similarities. At type 2; subluxations between 25% and 75%, we divided type II in two subgroups according to the angle between the inner margin of the teardrop and superior border of the acetabulum, at type IIa, the angle is less than 60°, at type IIb, the angle is greater than 60°, it’s important to show femoral allogreft usage requirement, at type 3; subluxations greater than 75%, at this type there will be no need of femoral allogreft usage but extra-small reamer usage for forming a suitable acetabular bed. At type 4; luxations greater than 100%, we also divided type IV in to two subgroups accordind to the distance between superior margin of true acetabulum and trochanter major line, at type IVa, < 2.5 cm, at type IVb, > 2.5 cm. It’s also important to make the decission of shortening. To form this classification three observers with different levels of training independently classified 412 dysplastic hips (operated between1995 and 2005) on 380 standard anteriorposterior pelvis radiographs, retrospectively according to the criteria defined by us. To assess intraobserver reliability, the measurement was repeated 3 months later. Statistical analysis was performed by calculating the weighted kappa correlation coefficient. System showed good inter- and intraob-server reliability for use in daily practice. Eventually, we determined a significant correlation between the aplied surgical procedures and classification. As a conclusion, we believe that our classification system of osteoarthritis secondary to developmental dysplasia of the hip in adult patients guides the surgical procedure more effectively than the other classification systems.