Two cases of fracture of the ulna with fracture-separation of the radial neck in children are presented. In one case there was no displacement of the radial epiphysis and in the other it was subluxated. The mechanism of injury is essentially a valgus strain on the extended elbow caused by a fall onto the out-stretched hand. Reduction of this fracture is difficult to attain by closed manipulation and may displace an undisplaced radial head. Open reduction is advisable and as the lesion is unstable, some form of fixation may be required; check radiographs of good quality are essential during the first 3 weeks. If reduction cannot be achieved and mal-union or cross-union is expected, it is preferable to put the hand in a neutral or a pronated position as it will be more useful than a hand fixed in supination.