Screening for oral cancer should be defined as the application of a test to people who are apparently free of disease to identify those who may have oral cancer and to distinguish them from those who may not. The aim of the test is not to be diagnostic but to identify changes that may be the earliest signs of impending disease. Defined in this way, screening is an ongoing public health measure, often funded by governments. A screening program must do no harm and must be cost effective. Governments demand that strict evidence of benefits and cost effectiveness be met before a program may be implemented. Although many studies have investigated the utility of potential screening tests, there have been few evaluations of screening programs and only one randomized controlled trial. Systematic reviews have concluded that there is insufficient evidence to show that oral cancer screening can reduce mortality from oral cancer, and to date, no country has implemented a formal oral cancer screening program. This paper reviews this evidence and tries to identify the barriers to screening and suggests areas of focus for future research.