AbstractThis article looks at the hospital as an expert system organized to promote distributed processes of collaborative medical problem solving. It is composed by subsystems and the collaborative processes resemble processes of socially distributed cognition. Terms like ‘medical discourse’ or ‘institutional interaction’ have been used to describe verbal activities in collaborative medical practice. But the definitions of these terms give a limited understanding of collaborative medicine. Observations of medical practice in a thoracic ward show that medical discourses work at institutional, professional, and moral levels. They deal with a multiplicity of problem types, involve a diversity of human and nonhuman agents, and take place within and generate complex layers of contexts. The development of the problem complex has to be professionally but subtly managed at an interactional level to reach conclusions that are institutionally, professionally, and morally acceptable. While extra-situational contexts may have a strong impact on these processes, medical problems are met and dealt with as concrete situational tasks, in restricted settings with different but concrete participants that operate within and generate local, linguistic, and interactional contexts.