The authors report a controlled trial to investigate whether knowledge of the severity of the outcome of a medical adverse event can influence expert judgment of its preventability. The authors obtained 21 standardized case abstracts in anesthesiology representing eight recognized classes of anesthetic complications. For each case, the authors prepared a matching case identical in every way, with the exception that if the true case resulted in mild reversible injury, the matching case was made to result in severe irreversible injury and vice versa. When reviewed by an expert panel of experienced anesthesiologists, the care in cases with a severe outcome was approximately 30% more likely to be judged as substandard in comparison with the identical case with a favorable outcome. The authors discuss the known weaknesses of expert review and implicit judgment and the implications of their data for quality assurance and other forms of care review.