Isolated palmar ulnar dislocation of the fifth carpometacarpal (CMC) joint is a rare injury which often yields only subtle radiographic findings that may be easily overlooked, especially when there is no associated fracture. We reported a case of an isolated palmar dislocation of the fifth CMC joint, diagnosed correctly by means of simple stress X-rays (traction and axial compression stress views). This method proved to be useful and needs no special equipment.