Abstract Reference to major arterial damage resulting from lumbar intervertebral disc operation is uncommon. Two such cases treated by us on the vascular surgery service are reported. In both, the common iliac artery was injured by capable and careful neurosurgeons fully aware of the possibility of such injury. The lesions were located within 2 to 3 cm. of the aortic bifurcation and followed exploration of the fourth-fifth lumbar intervertebral space. Both patients were salvaged by heroic surgery, but not without partial disability, one with residuals of hepatitis following multiple blood transfusions, and one with femoral nerve palsy and arterial insufficiency as a result of false aneurysmal formation and what was believed to be a breakdown in the homologous arterial graft. The relational anatomy of the lumbar vertebrae and contiguous major vessels is described and correlated with the potential types of vascular complications. Operation at the fourth-fifth lumbar intervertebral space and use of the pituitary rongeur are emphasized as being most commonly associated with these lesions. Immediate transabdominal exploration and arterial repair are recommended when this condition is confirmed or seriously suspected.