Dyschondroplasia is a retardation of the normal transformation of primordial cartilage into bone. In the three cases of dyschondroplastic bow legs presented, the process was limited to the region of the medial aspect of the upper tibial epiphysis. All of the patients were young girls in the first decade of life. In two of the cases, the condition was bilateral; in one, unilateral. A progressive and severe type of genu varum was the outstanding symptom. The roentgenograms showed typical changes in the region of the medial half of the upper tibial epiphysis. Microscopic section in the involved region of one of the patients showed a definite picture of dyschondroplasia.