Communication between people is commonly thought to play a major role in determining the success or failure of collaborative design projects. We conducted eight weeks of observation and 62 interviews in three design companies. Our findings indicate that communication is blamed for causing many problems which are not of an obviously technical nature. However, such problems are more often symptomatic of underlying factors related to information, representation, individual, team, and organisational issues. Examples of factors influencing communication at interfaces are people's understanding of the ‘sequence of tasks’ or ‘goals and objectives’ in the design process. With a system-theory informed conceptualisation of communication, we propose that awareness of such factors could assist design practitioners in targeting interventions and researchers in generating hypotheses about communication and design performance.