The natural course of "dysplasia" of the hip diagnosed between the age of two and ten months was followed in 47 children. If the dysplasia diagnosed by radiographs was not combined with a clinical instability of the hip dislocation never occurred although no therapy- except abduction exercise - was given. The radiological signs of dysplasia regularly disappear after the child has learned to walk. Three different kinds of dysplasia are described. Dysplasia may be a residual sign of neonatal instability which became stable with or without treatment. Pseudodysplasia is the effect of faulty X-ray technique or X-ray interpretation. In dysplasia with no known instability in the history it may be the residual sign of a neonatal instability which was not diagnosed or it may be a variation of development of the hip joint during the first year of life. Since dysplasia without clinical instability does not progress and will never end with a dislocation there is no indication for therapeutic measures in a stable hip with radiological signs of dysplasia during the first year of life. The treatment of unstable hips diagnosed between the third and the twelfth month of life may be dangerous due to epiphyseal damage by immobilisation.