Many people with severe disabilities also have severe communication impairment, meaning they lack sufficient speech and language to meet their everyday communication needs. This chapter first describes severe communication impairment and considers the distinction between the terms nonverbal and minimally verbal. Following this, we provide an overview of the nature and prevalence of severe communication impairment in people with different types of severe disability conditions. The main purposes and approaches for assessing communicative functioning in people with severe disabilities who are nonverbal or minimally verbal are then summarized. We conclude that comprehensive assessment using empirically validated instruments is a critical component in the overall communication intervention process.