It has been emphasized that the early diagnosis and treatment of congenital dislocation of the hip joint are very important to gain good resulfs since von Rosen has published a report on a mass screening of this disease. X-ray examination of the hip for the mass screening to diagnose the dislocated hips has been usually performed in Japan. However, the present author has carried out the mass screening by clnical examination because of difficulty in accurate diagnosis of dislocation as well as subluxation of the hips in the new born infants by X-ray picture and because of danger of irradiation. In the present study 4675 infants were examined by Ortolani's click sign, Barlow's test and flexion-abduction test at the fixed intervals of seven days, one month, three months, six months, twelve months and three years of age. The results were summerized as follows; 1) The incidence of congenital dislocation of the hip joint was 0.7 % , subluxation 1.0 % and dysplasia 2.2 % which had positive clinical tests at three months of age. 2) Both CE angle and acetabular roof obliquity in the hips with congenital dislocation, subluxation and dysplasia of the hip joint at three years of age were less than those of the normal hips with significant difference. 3) No congenital dislocation of the hip joint and subluxation were found in the cases which showed no clinical signs at the each check times. 4) From these findings it is suggested that X-ray examinations are necessary only in the cases with positive clinical signs at three months of age.