[Truncated abstract] Gastroenteritis is frequently associated with a food or water borne source and the investigation of such cases is undertaken to identify potential sources of infection. Where contaminated food or water are identified as the source of infection/intoxication, action may be taken to limit or prevent further people being affected, and in so doing limit costs to the health care system. This study was undertaken to determine if there is a more effective and efficient way to collect information from patients with certain enteric illnesses. This was based on a trial process of posting self-administered questionnaires with a reply-paid return envelope to the patient and compared with the existing process where local government Environmental Health Officers interview the patient and provide a report to the Department of Health. A limiting factor in the existing process is the time lapse between the onset of illness and follow-up by Environmental Health Officers (EHOs), which results in difficulties in contacting the patient and obtaining a dietary history. Furthermore, the existing system is resource intense, requiring officers to individually interview patients either in person or by telephone. The study was of those patients living in the Perth metropolitan area whose doctor notified the Department of Health that the patient had contracted any of three notifiable enteric illnesses (campylobacterosis, giardiasis or salmonellosis), and the patient was not part of a known outbreak and was assessed as not requiring urgent follow-up. The trial process was used for patients living in five local government areas and the return rate, timeliness of return and completeness of questionnaires in the trial process was compared with the reports returned under the existing process of investigation and reporting by EHOs from 24 metropolitan local government areas that were not part of the trial process. An estimate of the potential costs to local government and the Department of Health was undertaken for both the existing and trial processes of collecting information from patients. A survey of local government EHOs in the metropolitan area was also undertaken to assess the perception of EHOs about roles and responsibilities in the follow-up investigation, the use of the Enteric Disease Investigation Report (EDIR) and the limitations that they identified in the current investigation process.