Between 1970 and 1977, 64 patients with infected pseudarthrosis of the femur and tibia were treated with an interlocking nail. The type of primary treatment prior to the development of the infected pseudarthrosis was plate fixation in 21 femurs and seven tibias and conventional intramedullary nails in 16 femurs and 20 tibias. Fracture union was obtained in 34 of the 38 femoral infected pseudarthrosis (89.5%) and 19 of 27 tibial infected nonunions (62.5%) following interlocking nailing. Seven of the eight failures (87.5%) in the tibial group were the result of reoperation with interlocking nails following infected plate fixation. Following removal of the interlocking nail and treatment of residual infection, osteomyelitis was considered quiescent in 59 patients (35 femurs and 24 tibias) and active in five patients (two femurs and three tibias). Today, external fixation in combination with gentamicin-PMMA chains for local antibiotic treatment is used in the majority of such cases, because fracture instability and the chronic osteomyelitis can be treated simultaneously.