A number of textbooks and professional volumes in applied behavior analysis suggest that interventions designed primarily to decrease a problem behavior should routinely be accompanied by efforts to increase the frequency of at least one appropriate behavior. Some sources describe the objective of this tactic as "replacing" the problem behavior. This paper considers rationales that might underlie this advice, as well as reasons why a general rule to this effect is inappropriate. This review reveals that although there may well be good reasons for considering this tactic, their rationales are often not well articulated and may even be unsound. It is also the case that there are good reasons why this tactic may not always be necessary, thus conflicting with an argument for a general rule. (Contains 1 note.)