Spinal cord injury has been recognized as a complication of cervical transforaminal injections, but the mechanism of injury is uncertain. In the course of a transforaminal injection, an observation was made after the initial injection of contrast medium. The contrast medium filled a radicular artery that passed to the spinal cord. The procedure was summarily abandoned, and the patient suffered no ill effects. This case demonstrates that despite using careful and accurate technique, it is possible for material to be injected into a radicular artery. Consequently, inadvertent injection of corticosteroids into a radicular artery may be the mechanism for spinal cord injury following transforaminal injections. This observation warns operators to always perform a test injection of contrast medium, and carefully check for arterial filling using real-time fluoroscopy with digital subtraction.