We evaluated the effectiveness of functional communication training (FCT) in reducing problem behavior and in strengthening alternative behavior when FCT was implemented without extinction. Following the completion of functional analyses in which socialpositive reinforcement was identified as the maintaining variable for 5 participants' selfinjurious behavior (SIB) and aggression, the participants were first exposed to FCT in which both problem behavior and alternative behavior were reinforced continuously (i.e., on fixed-ratio [FR] 1 schedules). During subsequent FCT conditions, the schedule of reinforcement for problem behavior was made more intermittent (e.g., FR 2, FR 3, FR 5, etc.), whereas alternative behavior was always reinforced according to an FR 1 schedule. Results showed that 1 participant's problem behavior decreased and alternative behavior increased during FCT when both behaviors were reinforced on FR 1 schedules. The remaining 4 participants shifted response allocation from problem to alternative behavior as the schedule of reinforcement for problem behavior became more intermittent. These results suggest that individuals might acquire alternative responses during FCT in spite of inconsistencies in the application of extinction, although even small errors in reinforcement may compromise treatment effects.DESCRIPTORS: functional analysis, functional communication training, intermittent reinforcement, extinction, self-injurious behavior, aggression Functional communication training (FCT;Carr & Durand, 1985) has become a popular treatment for behavior disorders in individuals with developmental disabilities. FCT typically contains two procedural components characteristic of a differential-reinforcement-of-alternative-behavior (DRA) contingency: (a) Reinforcement for problem behavior is discontinued (extinction), and (b) an alternative behavior is prompted or shaped using the same reinforcer that maintains problem behavior (reinforcement of an alternative mand).A great deal of emphasis has been placed This research was supported in part by a grant from the Florida Department of Children and Families. We thank Juliet Conners for her assistance in conducting this project. SungWoo Kahng is now at the Kennedy Krieger Institute, Johns Hopkins University School of Medicine.Reprints may be obtained from Brian Iwata, Psychology Department, The University of Florida, Gainesville, Florida 32611.on the reinforcement component of FCT, yet results from several studies indicate that the extinction component may be just as important to the success of FCT interventions. For example, Shirley, Iwata, Kahng, Mazaleski, and Lerman (1997) compared the effectiveness of FCT with and without extinction in decreasing self-injurious behavior (SIB) and in establishing an alternative response (a manual sign) with 3 participants. During FCT without extinction, when both SIB and signing produced access to reinforcement on a continuous basis (i.e., a fixed-ratio [FR] 1 schedule), all participants continued to exhibit high rates o...