Although individuals may engage in several topographies of aberrant behavior, each with different functions, it is not uncommon for researchers to conduct one functional analysis. We conducted two functional analyses for a child with autism, one with and one without consequences for stereotypic vocalizations. Only the analysis without consequences for stereotypic vocalizations differentiated the function of the primary target behavior, disruption. The data suggest that in some cases high-rate behaviors may serve as establishing operations that mask the function of lower rate behaviors and warrant separate functional analyses. (Contains 1 figure.)