Individuals with severe disabilities often experience difficulties in acquisition of proper communication skills due to their physical or intellectual deficits. Current study findings suggested positive results of Augmentative and Alternative Communication(AAC) intervention for those with severe disabilities. According to ASHA(1991), the AAC system can be defined as an integrated group of components, including the symbols, aids, strategies, and techniques used by individuals with severe expressive communication disorders to enhance communication. There are unique issues and procedures in augmentative and alternative communication assessment. The purpose of this article is to investigate and explain the AAC assessment process and current issues. First, we summarized the purpose and general principles of AAC assessment. These reveal the basic philosophy of AAC assessment. Second, we studied development of AAC assessment models. Third, we discussed specific components of recent AAC assessment model (participation Model), which included 1) identification of participation pattern and communication need, 2) assessment of opportunity barriers, and 3) assessment of access barriers. Finally, implications and directions for future research and practice are also discussed.