Communication between medical and dental practitioners about patients they have in common enhances total patient care, but such communication rarely occurs. This may be due to lack of appreciation by doctors of the medical risks to certain patients undergoing dental treatment. To ascertain a relevant medical history, prospective medical screening was performed on 1500 new patients attending a general dental practice using a standard health questionnaire followed by an interview between the patient and dentist. There were 382 (25.5%) patients with a current or past medical history of relevance to dentistry, 90 (6.0%) were taking medication of potential importance and 105 (7.0%) considered they had an intolerance to certain drugs. The screening provided a patient data base for medical and medico-legal purposes. A total of 376 (25.1%) questionnaires were filled out incorrectly and 63 of these (16.8%) had major misinformation about medical history. A small but important group deliberately misled the dentist either from fear of refusal of treatment or embarrassment about their medical history. Therefore interviews are an essential adjunct to written health questionnaires in eliciting accurate information. Formal screening of new patients is essential in general dental practice. Furthermore, general medical practitioners need to become aware of the common risks to patients undergoing dentistry. Better formal and informal communication between general medical and dental practitioners is recommended for the benefit of their mutual patients.