This paper describes the assessment of communication skills in 120 adults with severe to moderate learning difficulties. Each subject was assessed on the Communication Assessment Profile (CASP), a new communication assessment procedure for use with this client group. Qualitative and quantitative comparisons were made between three different methods of assessment used in CASP. These included observational assessment, elicited conversation and a structured language task. The relative usefulness of each method was evaluated, and the implications for communication assessment outlined.