The paper presents the results of surgical stabilization of pseudoarthrosis of long bone augmented by a transfer of in vitro cultivated bone marrow interstitium cells in 4 patients. In three cases a Zespol external fixation device was applied without opening the pseudoarthrosis. One patient was treated by open reduction of the bone fragments with the use of frozen spongiose bone grafts. The mean age of the patients was 30.2 years. In two cases the pseudoarthrosis had developed in the tibia, in the remaining two cases it developed in the ulna. The pseudoarthrosis was present for a mean time of 2.5 years. In all cases healing of the pseudoarthrosis was observed after a mean time of 3.7 months.