When standard analogue functional analysis procedures produce inconclusive results in children with conversational speech, the child's mands may help to identify the function of destructive behavior. In the current investigation, functional analyses conducted with 2 children who exhibited self-injury, aggression, and property destruction were undifferentiated across conditions. Based on informal observations and school and parental report, an analysis was conducted using mands to help determine the function of the destructive behavior. Using a multielement design, the therapist's compliance with the child's mands occurred either on a fixed-ratio (FR) 1 schedule or contingent on destructive behavior. Destructive behavior occurred at high and consistent levels when reinforcement of mands was contingent on destructive behavior and at near-zero levels when reinforcement of mands occurred on the FR 1 schedule. Based on these results, a second analysis was conducted in which compliance to mands occurred only when the child appropriately requested it (i.e., functional communication training plus extinction) and, for 1 child, compliance with mands was terminated contingent upon destructive behavior (i.e., functional communication training plus response cost). For both children, the rates of destructive behavior decreased markedly. The results suggest that assessing the child's mands may be useful in decreasing destructive behavior when a functional analysis is inconclusive.