Abstract Individuals with severe disabilities whose speech is either ineffective or inefficient for meeting their communicative needs have benefited from augmentative and alternative modes of communication (AAC). However, despite the evidence supporting the use of AAC with individuals with severe disabilities, practitioners still encounter challenges in implementing AAC interventions. These challenges be due, in part, to problems related to contextual fit. This paper (a) examines the importance of contextual fit in the design and implementation of AAC interventions, (b) explores the potential role of response efficiency for enhancing contextual fit, (c) presents a framework for examining the response efficiency of AAC interventions, and (d) provides a discussion of needed research. Keywords: Augmentative and Alternative Communication, AAC, Contextual Fit, Response Efficiency. Introduction Augmentative and Alternative Communication (AAC) refers to the use of devices or techniques that supplement or replace an individual's spoken communication skills (Mustonen, Locke, Reichle, Solbrach, & Lindgren, 1991). AAC includes unaided modes of communication (e.g., gestures, sign languages/systems, and facial expressions) as well as aided modes of communication (e.g., line drawings on a communication board, written words on a pad of paper, laptop computers with synthesized speech output, dedicated AAC devices with digitized speech output). Individuals with severe disabilities whose speech is either ineffective or inefficient for meeting their communicative needs have benefited from augmentative and alternative modes of communication (e.g., Cafiero, 1998; Johnston, McDonnell, Nelson, & Magnavito, 2003; Johnston, Nelson, Evans, Palazolo, 2003; Marcus, Garfinkle, & Wolery, 2001; Mirenda & Ericson, 2000; Quill, 1997; Rowland & Schweigart, 2000; Schopler, Mesibov, Shigley, & Hearsey, 1995). However, as promising as the evidence supporting the use of AAC with individuals with severe disabilities has been, practitioners still encounter challenges in implementing AAC interventions. These challenges be due, in part, to problems related to contextual fit. This paper (a) examines the importance of contextual fit in the design and implementation of AAC interventions, (b) explores the potential role of response efficiency for enhancing contextual fit, (c) presents a framework for examining the response efficiency of AAC interventions, and (d) provides a discussion of needed research. Importance of Contextual Fit in the Design and Implementation of AAC Interventions The term contextual fit refers to the compatibility between an intervention and a variety of variables, including characteristics of the person for whom the intervention was developed, characteristics of the individuals who will implement the plan, and features of the environment within which the intervention will be implemented (Albin, Lucyshyn, Horner, & Flannery, 1996). Albin et al (1996) posit that an intervention may be theoretically well designed and solidly grounded in both behavior theory and documented practice, and yet still not be a good fit for the people and the environments involved (p.83). An intervention lack strong contextual fit for a variety of reasons. For the AAC user, the AAC intervention require too much effort and/or not consistently result in interactions that fulfill their communication wants/needs. For communication partners, the AAC intervention be cumbersome or time consuming to design and implement, conflict with existing priorities, or fail to meet their own communicative needs. Personal experience suggests that many AAC users and their communication partners have participated in interventions that lack a good contextual fit. For example, consider Jane, a preschool aged child who was taught to use sign language to communicate her wants and needs. …