Objective: To compare four health professions' attitudes towards interprofessional collaboration (IPC) and their evaluations of a programme aimed at enhancing IPC across a health system. Design: Questionnaire survey. Setting: Australian Capital Territory health services. Participants: Sample of medical (38), nursing (198), allied health (152) and administrative (30) staff. Intervention(s): A 4-year action research project to improve IPC. Main Outcome Measure(s): Questionnaire evaluating the project and responses to the 'Attitudes toward Health Care Teams' and 'Readiness for Interprofessional Learning' scales. Results: Significant professional differences occurred in 90% of the evaluation items. Doctors were the least and administrative staff most likely to agree project aims had been met. Nurses made more favourable assessments than did allied health staff. Doctors made the most negative assessments and allied health staff the most neutral ratings. Improved interprofessional sharing of knowledge, teamwork and patient care were among the goals held to have been most achieved. Reduction in interprofessional rivalry and improved trust and communication were least achieved. Average assessment of individual goals being met was agree (31.9%), neutral (56.9%) and disagree (11.2%). On the two attitude scales, allied health professionals were most supportive of IPC, followed by nurses, administrators and doctors. Conclusions: Although overall attitudes towards IPC were favourable, only a third of participants reported that project goals had been achieved indicating the difficulties of implementing systems change. The response profiles of the professions differed. As in the previous research, doctors were least likely to hold favourable attitudes towards or endorse benefits from social or structural interventions in health care. © The Author 2012. Published by Oxford University Press in association with the International Society for Quality in Health Care; all rights reserved.