Discrete-trial functional analysis (DTFA) is an experimental method for determining the variables maintaining problem behavior in the context of natural routines. Functional communication training (FCT) is an effective method for replacing problem behavior, once identified, with a functionally equivalent response. We implemented these procedures in the natural environment for three individuals with developmental disabilities who resided in a residential treatment facility. Study 1 results show that the DTFA procedures experimentally validated the function of each participant's problem behavior after completing a functional assessment using informal and descriptive methods. Study 2 results reveal that FCT was successful at replacing problem behavior with an alternative communication behavior that served the same function. A unique feature of this study was the use of behavioral indication (i.e., observable behavior signaling momentary motivation) as a cue for determining when to deliver the FCT intervention.