Fractures of the lateral humeral condyle run a great risk of subsequent displacement. This is also true--although to a lesser extent--for primarily non-displaced or minimally displaced (less than or equal to 2 mm) fractures. The present retrospective investigation aimed at defining radiographic criteria in order to predict the stability of non-displaced or minimally displaced fractures in 159 children. The fractures were classified according to radiographic criteria into 3 groups considered to represent stable, ambiguous and unstable fractures. Additional displacement while immobilized in plaster occurred in 2.6 per cent of the fractures classified as stable and in 44.4 per cent of those classified as unstable (p less than 0.001); in the ambiguous group subsequent displacement occurred in 24.1 per cent. It is concluded that the radiographic criteria should be useful to predict the stability of non-displaced or minimally displaced fractures of the lateral humeral condyle in children.