The interdependencies of Pharmacy and Therapeutics Committee members in 222 teaching hospitals were studied by use of the social relations model. Cooperation, influence, frustration and enjoyment were studied among four-person subgroups chosen from the five roles recommended for hospitals by the American Society of Hospital Pharmacists: physician-chair, physician-nonchair, pharmacist, nurse and administrator. The results show that the elicitation and reception of cooperation, influence, frustration and enjoyment vary considerably by role (as manifest in actor and partner effects); small amounts of individual reciprocity (i.e. the association between actor and partner effects) were found for some measures of interdependence across roles, while small amounts of dyadic reciprocity (i.e. the association between reciprocal relationship effects) were found for many relationships. Significant group level (i.e. committee) effects were found as well.