Two types of interlocking intramedullary (IM) nails and a noninterlocked IM nail were tested in bending and torsion, to compare their flexural stiffness, and torsional stability in a femoral fracture model. A Grosse-Kempf IM nail with proximal and distal cortical interlocking screws, a Brooker-Wills IM nail with proximal interlocking screw and distal cancellous interlocking fins, and a Grosse-Kempf IM nail with no interlocking screws were tested. All IM nails had similar flexural stiffnesses. The interlocked Grosse-Kempf IM nail was most stable in torsion, followed by the interlocked Brooker-Wills IM nail. The noninterlocked Grosse-Kempf IM nail was least stable in torsion.