The accounts given of the standard "ad hominem" fallacy in logic textbooks raise three interesting and important issues for teachers of critical reasoning skills. Firstly, the standard definition, explanation and examples of the "ad hominem" fallacy seriously distort the manner in which this type of argument is effectively used in the complex world of actual argumentation. Secondly, the teaching of textbook examples tends to be misleading at best and most probably inhibits students from developing good critical reasoning skills. Thirdly, the "ad hominem" approach is a useful and important means of deciding what to believe and how to act in real-life situations. Unfortunately, the "ad hominem" argument has come to represent an idealised caricature of how this argument form can be abused or used wrongly. Due to the need for simplification, logic texts have erroneously characterised this mode of argument as always a serious rational misperformance. This paper, then, has two broad aims. Firstly, it attempts to undermine the standard account of the "ad hominem" fallacy by showing that teaching the standard textbook accounts to students is counterproductive to developing critical reasoning skills. Secondly, it offers two arguments (the practical and epistemological positions) against the standard definition of the "ad hominem" and suggests a new account of what students ought to be told about the "ad hominem" mode of argument. The author discusses the impact of teaching the standard "ad hominem" fallacy and examines the "common sense" strategy which many students develop for assessing real arguments. He also outlines and discusses his arguments supporting the claim that the "ad hominem" argument is very often not a case of rational misperformance. (Contains 27 notes.)