Oral cancer has increased recently in Australia, and overall survival rates have not improved in the past 30 years. Dentists are uniquely well placed to screen their patients at regular recall examinations and detect cancers or pre-cancerous lesions at an early curable stage. Although the major risk factors--tobacco smoking and alcohol abuse--have been identified, only a minority of patients at-risk will develop oral cancer. Molecular analysis has now detected an accumulation of genetic lesions in oral cancer, but the earliest molecular changes in the oral epithelium in the progression to malignancy in at-risk patients has not yet been determined. These changes could if known be exploited for screening purposes. How long human oral carcinogenesis takes to progress from the initiated cell to an invasive tumour, and whether molecular biology can be used to identify the minority of patients who will develop cancer from the large population exposed to the risk factors, are other important unanswered questions. p53 tumour suppressor gene mutations are the most frequently found genetic errors in oral cancer and the p53 gene is a likely target for tobacco and alcohol.