There are few reports in the literature on nonunion of the fibula following simultaneous fracture of the tibia and fibula. They apparently develop in cases where when only the tibia is stabilized and early functional treatment follows. Six patients suffering from painful nonunion of the fibula were treated in our trauma center from 1985 to 1987. Primary fixation was achieved with a plate in three cases, external fixation in two, and a Küntscher nail in one case. Because of infection, the nail was replaced by external fixation after 2 weeks. After healing of the tibia, the patients developed pain during normal use, and there was local tenderness, edema, and paresthesia. In all cases the X-ray films showed hypertrophic nonunion of the fibula. Four patients were treated with plate osteosynthesis of the fibula, which alleviated the problems. From our retrospective data we conclude that in primary therapy of lower leg fractures, plate fixation of the fibula should also be included in cases where the fractures are located in the distal half of the lower leg and show signs if instability due to displacement, oblique fracture forms, and multiple fragments.