The present paper treats the problem of the lengths' difference of legs in view of the general physician. After a five years' research a survey has been established and a classification in four groups has been made. Moreover the question of diagnosis and therapy has been treated. The requirement has been raised to diagnose as early as possible and to apply the corresponding therapy even in case of a lengths' difference below 20 mm in order to avoid any inevitable secondary consequences. Only by acting this way arising complaints, long working incapabilities and last but not least considerable expenses can be prevented.