Research has shown that different maladaptive behavior categories may be maintained by different contingencies. We examined whether behavior categories or behavior topographies determine functional properties. The "Questions about Behavioral Function" with its five subscales ("Attention", "Escape", "Nonsocial", "Physical", and "Tangible") was completed by direct care staff for one target behavior for each of 115 adults with varying degrees of intellectual disabilities. In the first step we examined the functional properties of three broad behavior categories (self-injurious behavior [SIB], stereotypic behavior, and aggressive/destructive behavior). Consistent with previous research stereotyped behaviors and SIB had significantly higher QABF "Nonsocial" (i.e., automatic positive reinforcement or self-stimulation) subscale scores than aggressive behavior, while none of the other subscales showed differences across the three behavior categories. Contrary to earlier studies, escape (or negative social reinforcement) was an important function not only for aggressive behavior, but also for SIB and stereotypies. A second analysis examined functional properties depending on two factors: the behavior topography (hitting vs. non-hitting behaviors) and their respective behavior category (SIB vs. aggression). SIB topographies had higher ratings than aggressive behavior on the QABF "Nonsocial" subscale. Of the five QABF subscales, only the subscale "Nonsocial" differed between categories of maladaptive behavior. Furthermore it was the behavior categories rather than the topographies that determined functional properties. (Contains 3 tables and 2 figures.)