Inattentional blindness occurs when individuals miss an unexpected event due to competing attentional tasks.  This study asked anesthesiologists to review the anesthetic management of five simulated cases, one of which included the image of a gorilla in the radiograph, to evaluate inattentional blindness. Only 4.9% of social media respondents reported an abnormality, suggesting that inattentional blindness may be common; the authors suggest several strategies to reduce this error.