Communication assessment of people with profound intellectual and multiple disabilities (PIMD) has seldom been investigated. Here, we explore approaches and decision making in undertaking communication assessments in this group of people. A questionnaire was sent to UK practitioners. The questionnaire elicited information about assessment approaches used and rationales for assessment choices. Fifty-five speech and language therapists (SLTs) responded. Findings revealed that the Preverbal Communication Schedule, the Affective Communication Assessment and the Checklist of Communication Competence were the most frequently used published assessments. Both published and unpublished assessments were often used. Rationales for assessment choice related to assessment utility, sensitivity to detail and change and their applicability to people with PIMD. Underpinning evidence for assessments was seldom mentioned demonstrating the need for more empirical support for assessments used. Variability in practice and the eclectic use of a range of assessments was evident, underpinned by practice-focused evidence based on tacit knowledge.