A study on the deformity of the hip in Legg-Calve-Perthes disease has been confined to the involved hip. Recently the morphological change of uninvolved hip has been investigated with histological and radiological means, by several authors. Their results, however, were inconclusive and there were much differences as to the pattern and incidence of abnormality. To elucidate and gain further insight into this differences, the authors have performed radiological observation on the opposite hip in 126 unilateral Legg-Calve-Perthes disease and have compared with that of normal 94 children. The results were as follows: 1. Surface irregularity; Surface irregularity was observed in both the disease group and the control group. The appearance rate in disease group (12.7%) was about two times that of control group (6.4%). 2. Thickness of articular cartilage: A change of thickness of articular cartilage was not observed. 3. Epiphyseal index; A statistically significant decrease in the disease group was observed with average epiphyseal index of 0.44±0.065 in the disease group and 0.50±0.095 in the control group respectively. 4. In conclusion, the authors could confirm the presence of more abnormality in the opposite hip of unilateral Legg-Calve-Perthes disease than previous recognition and became to have question on the reliability of the opposite hip as a normal reference in measuring the various quotients.