Four typical cases of dysplasia epiphysealis hemimelica are reported, the age when first examined varying from 18 months to 5 years. The observation periods varied from 3-20 years. After fusion between the accessory ossification centres of the osteochondroma and the regular epiphysis, no further enlargement was observed. In three cases an enlarged medial femoral condyle was resected, in two cases the resection was done through bone, leaving a non-cartilaginous surface in the knee joint. This procedure seems to have no harmful consequences; one of the patients seen 19 years later had no complaints, and the knee joint appeared almost normal on X-rays.