The deformity of the hip in Legg-Calve -Perthes disease has been a subject of extensive investigation, because it is a significant risk factor in the development of osteoarthritis. In the bulk of the studies, the deformity was observed at primary healing stage or thereafter, since it could easily be recognized on the plain roentgenogram. Recently the morphological changes at the earlier stages of the disease have been investigated with the aid of bilateral arthrography, by several authors. Their results, however, were inconclusive and there were much differences as to the exact time of onset and the cause of the deformity. To elucidate and gain further insight into these differences, the authors have performed bilateral arthrography in 20 unilateral disease and have reviewed the early morphological changes of the epiphysis and labrum. The results were as follows: 1. Epiphyseal width: In most patients an increase in epiphyseal diameter was observed in both the avascular and fragmentation stages. Exceptions were seen in one case on anteroposterior film and two cases on forg-lateral film. The extent of increase was mild in the avascular stage: average of 5.9% and 4.0% in antero-posterior and frog-lateral films respectively. The increase became more pronounced in the fragmentation stage, 13.7% and 13.9% respectively, in the two projections. 2. Epiphyseal height: A decrease in epiphyseal height was observed in all films without exception. The amount of decrease was on the average 12.2% each in both projections in the avascular stage, as evidenced by 25.4% and 25.7% in each of the two projections. 3. Proximo-lateral shift of lateral labral apex of acetabulum: The morphological deformation as seen on the arthrogram was detected by measuring the positional shift of the lateral labral apex of acetabulum. The average shift in the avascular stage was 2.2mm proximally, and 1.7mm laterally, and as for the fragmentation stage, the shifts were 4.7mm and 2.1mm respectively. 4. In conclusion, the authors have demonstrated that deformation of both the epiphysis and acetablulum develops early, even in the stage of avascular necrosis and that the decrease in epiphyseal height is possibly contributing to the increase in its diameter(coxa magna).