To encourage the public to attend and accept oral cancer screening, further understanding is required of the ability of structured information to alter patient knowledge. Some evidence has been reported to show that knowledge about oral cancer is improved, especially in smokers with written information. Objective: To test if a patient information leaflet (PIL) would have a differential effect on knowledge dependent on current or past smoking behaviour. Method: Patients (N=995) attending 20 general dental practices in Northern Ireland were invited to participate, 28 refused (response rate= 97%). Patients were randomised into two groups. The experimental group received a PIL and then completed a self-report questionnaire, whereas the control group followed same procedure without the PIL. Measures included a 36 item oral cancer knowledge scale. Results: Usable data were available from 944 patients; mean (SD) age= 42 (15), 65% female. A clear benefit of the PIL on patients’ oral cancer knowledge was found, particularly for smokers and those with a history of smoking. Conclusion: These findings demonstrate that public awareness of smokers can be raised with written information.