This case series reports on 4 patients in whom intraoperative penetration of the femoral cortex occurred and went unrecognized on routine postoperative radiographs. This case series highlights some important points. Femoral cortex penetration can and does occur with uncemented hip arthroplasty and is likely to occur when surgical exposure is difficult and inadequate (such as in patients with severe obesity) or some form of proximal femoral deformity exists (such as patients with achondroplasia). Extra diligence should be exercised to avoid this complication in the high-risk patients, and adequate 2-plain radiographs may need to be ordered intraoperatively if such complication is suspected.