Augumentation shelf operation of acetabulum, modified by senior author after Ghormley(1931) and Staheli(1981) procedures was performed on 6 patients(8 hips) for dysplastic hip in the adolescents and young adults during the period from September, 1993 to May, 1994 at Guro hospital, the Korea University, College of Medicine. The results of cases which could be made of follow up more than one year were assessed from the point of view of function, relief of pain and progression of arthritic change as demonstrated radiologically. Material consists of two males(2 hips) and four females(6 hips). The mean age at operation was 22 years 6 months(range 10 years 3 months to 34 years) and mean follow up 2 years 7 months(range 14 month to 8 years 4 months). The preceding diagnoses were acetabular dysplasia in four hips, dysplatic hip after developmental dislocation of the hip joint in three hips and Legg-Perthes residual in one hip. According to criteria for clinical and radiological assessments(Charnley 1972, Summers 1988), all of the eight hips were graded as of good result. Results of present study seem suggestive of the fact that augumentation shelf operation of acetabulum is an effective and safe precedure for residual hip dysplasia.