Three cases of anterior distal femoral cortex penetration during intramedullary nailing for subtrochanteric fractures are documented. Case 1 involved a Zimmer (Warsaw, IN) M/DN antegrade femoral nail, case 2 a Howmedica (Allendale, NJ) long-stem Gamma nail, and case 3 a Synthes (Paoli, PA) titanium femoral nail with spiral blade locking. The anterior Zimmer nail penetration resulted in a displaced supracondylar fracture, which subsequently required revision. The Gamma nail as well as the Synthes nail were left impaled through the distal femoral cortex, and the subtrochanteric fractures went on to union. The anteroposterior radius of curvature for the Zimmer, the long Gamma, and the Synthes nail are 257 cm, 300 cm, and 150 cm, respectively. It has been estimated that the radius of curvature of the femoral diaphyseal canal is 114 to 120 cm. It appears that the difference in femoral anteroposterior bow between the bone and the implant is a contributing factor to distal femoral anterior cortex penetration in intramedullary nailing of subtrochanteric fractures.