BACKGROUND We sought to determine the impact of general practitioner communication on the efficient management of patients who present to the emergency department. Casemix, severity, time of presentation, the quality of the letter and the reception of a telephone call were considered. METHODS All consecutive patients presenting to the emergency department of Mornington Peninsula Hospital (Frankston) for one month in 1992 were included in this survey. The methodology is summarised in Figure 1. RESULTS The referral letter made no difference to patients' waiting time and time spent in the department and a non significant difference in communication back to the general practitioner. This was found despite the quality of the referral letter, the time of presentation, and the diagnosis. The general practitioners' telephone call, however, decreased significantly the patient's waiting time. Investigations that were reported in the general practitioners' letters and not repeated by the emergency department resulted in a direct saving of $2604 for the month of the study. High interrater reliability was discovered in the rating of letters by six general practitioners. CONCLUSIONS Despite the ability of general practitioners to select appropriate cases for referral, only the telephone call results in a quantifiable benefit for patients who attend their general practitioner. The high inter-rater reliability affirms the use of referral letters as audit tools in general practice. Better practical use could be made of general practitioners' referral communication to the emergency department.