Using a postal questionnaire, we studied the types of problems that general practitioners encounter in the communication with internal medicine consultants, and the consequences that occur as a result of these problems. Possible solutions to these problems were analysed, especially the use of electronic mail. The questionnaire was sent to 363 general practitioners in two regions in The Netherlands; replies were received from 144 (40%). Of these, 47 (33%) reported a total of 82 communication problems with the internist concerning the patient described in the most recent letter received from an internist. The most frequently reported problems were: failure of the internist to report in good time when referring the patient back to the general practitioner (15; 10%); failure of the internist to provide sufficient detail in intermediate reports (15; 10%). In 39 of 47 patients in which problems occurred, these problems led to a total of 58 consequences. The most frequently reported consequences were irritation caused to the general practitioner (15; 10%) and irritations caused to the patient (13; 9%). We conclude that communication problems mainly arise from too late delivery of information, and a lack of understanding by the internist of the information needs of the general practitioner. Personal contacts between co-treating physicians and well-established protocols are key elements in providing good cooperation between physicians. Electronic mail may be a good option to assist physicians in maintaining protocol-based communication.