Functional analysis (FA) methodology is the most precise method for identifying variables that maintain problem behavior. Occasionally, however, results of an FA may be influenced by idiosyncratic sensitivity to aspects of the assessment conditions. For example, data from several studies suggest that inclusion of a tangible condition during an FA may be prone to a false-positive outcome, although the extent to which tangible reinforcement routinely produces such outcomes is unknown. We examined susceptibility to tangible reinforcement by determining whether a new response was acquired more readily when exposed to a tangible contingency relative to others commonly used in an FA (Study 1), and whether problem behavior known not to have a social function nevertheless emerged when exposed to tangible reinforcement (Study 2). Results indicated that inclusion of items in the tangible condition should be done with care and that selection should be based on those items typically found in the individual's environment. (Contains 1 table and 2 figures.)