BACKGROUND: A "peripheral IJ" is a 2.5-in angiocatheter placed in the internal jugular vein with ultrasound guidance but typically no barrier precautions. Previously published literature has shown safety with none to minimal complications. CASE REPORT: This report describes 2 cases of iatrogenic pneumothorax that occurred during this procedure. One was caused by an emergency medicine intern, the other by an experienced faculty member. Both occurred in petite women with low body mass indices. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: It is important to remember that there are risks inherent with using the internal jugular vein for intravenous access. Particular vigilance should be used with patients who are thin.