Concomitant physeal fractures of the distal femur and proximal tibia are very rare in children and adolescents. They are included in the classification of the "floating knee" injuries. Two cases with this combined injury are reported. They were closed injuries and in both patients the fracture of the proximal tibial epiphyseal plate was nondisplaced. In the first, a six-year-old girl, an early diagnosis was made radiographically. The intra-articular femoral fracture was operatively reduced and fixed. No growth abnormality was encountered 12 years later. The second patient, a 16-year-old boy, was conservatively treated for a displaced fracture-separation of the distal femoral epiphysis. Four weeks later there was physeal widening on both sides of the knee which indicated an associated fracture of the proximal tibial epiphyseal plate. One year after injury there was a varus deformity of the knee that was treated with a corrective osteotomy. Ten years later there is normal alignment of the leg.