Background: General practitioners integrate an array of social and environmental factors into their prescribing decisions. In teaching hospitals, despite the involvement of multiple practitioners in making and acting on prescribing decisions, little is known about the influence of roles, relationships, professional subcultures and underlying beliefs, on prescribing practices. Aim: To explore the social and cultural dynamics of prescribing in teaching hospitals. Method: Consultants, registrars, junior doctors, nurses and pharmacists from 2 large Sydney teaching hospitals were sampled purposively and invited to participate in a qualitative study involving semi-structured interviews. The interview topics explored included: attitudes about prescribing, roles and responsibilities, communication of decisions, influences on prescribing and factors contributing to prescribing errors. Interviews were transcribed verbatim and the content analysed thematically. Results: Participants included 8 consultants, 8 registrars, 9 junior doctors, 7 nurses and 11 pharmacists. 5 distinct sets of social and cultural influences on prescribing behaviours were identified. The dominant set of influences related to the structure of how prescribing took place and chief among these were the strong intra-professional relationships of medical teams. Other social and cultural influences related to how prescribing decisions were communicated, underlying assumptions within medical teams, knowledge acquisition and the hospital environment. Conclusion: Prescribing in teaching hospitals is shaped by a complex web of social and cultural dynamics. An appreciation of these influences may be vital to the success of strategies to improve use of medicines in teaching hospitals. J Pharm Pract Res 2008; 38: 286-91.