The principal aim of this study was to describe the frequent errors that are being committed when treating congenital pseudarthroses of the lower leg. The authors studied this in 25 patients. 21 of these were referred to surgery, whereas 4 were presented by colleagues seeking counsel and were then subjected to further treatment at another location. One-half of the 21 congenital pseudarthroses had already been unsuccessfully operated on in other hospitals up to as often as four times. The method of "combined plate osteosynthesis" was employed with 19 of the 21 patients; this method was originally developed by W. Blauth and used for the first time in 1969. Witt and Refior reported on a similar technique at about the same time and independently thereof. 17 of our patients were cured; 2 failures cannot be blamed on the method. The main procedural error in the previously operated patients had been a misjudgement of the disease pattern which is characterised by "biological deficiency" and lack of load-bearing capacity of the bones of the lower leg in a circumscribed region at the transition from the median to the lower third of the lower leg. Another important factor was certainly the lack of knowledge of the pathogenetic significance of the pathologically affected periosteum. In this connection the failures were certainly also conditioned by faulty osteosyntheses resulting therefrom, without using autologous osseous material for grafting; by operating too early; by immobilising the limbs postoperatively for too short a period; and by insufficient relief of the limbs before a patent medullary cavity had formed. Another error consisted in omitting to perform autologous bone chip implantation at the same time when removing osteosynthesis material. The authors conclude that congenital pseudoarthroses of the lower leg can in all probability be remedied already in early childhood if the well-tried principles of treatment of "combined plate osteosynthesis" are observed. This, however will not result in normal lower leg bones, as can be concluded from the fact that spontaneous fractures have occurred partly even in the locomotor apparatus after the pseudarthroses had healed. In future, petiolated bone grafts performed by microsurgeons should be promising and competitive. Küntscher nail osteosyntheses should also offer good chances of healing if performed from the site of the sole. Their main drawbacks might be damage of the distal tibial epiphysis and of the functions of the ankle joint and talo-calcaneonavicular joint.