The authors assessed the effects of using "none of the above" as an option in a 40-item, general-knowledge multiple-choice test administered to undergraduate students. Examinees who selected "none of the above" were given an incentive to write the correct answer to the question posed. Using "none of the above" as the keyed option made items much more difficult (d = -1.11). Furthermore, 45% of the time that examinees correctly selected "none of the above," they wrote either a wrong answer (19%) or no answer (26%), and rescoring items to deny credit in these cases caused item discrimination to fall (d = -0.35). Thus, when "none of the above" is the keyed option, credit earned by examinees with knowledge deficiencies can make items appear to have more discriminatory power than is actually the case. The authors recommend that "none of the above" should not be used as an option in multiple-choice items.