Oral submucous fibrosis (OSMF), a precancerous condition of the oral cavity, has been studied by a number of workers in the field. The available epidemiological data showed a clear-cut geographical and ethnic predisposition, which suggested that certain customs/habits prevalent among the population groups in south-east Asia might be possible etiological factors. However, none of these customs was shown to be causally linked and the association in many cases was 'casual'. This led some workers to consider the importance of systemic predisposition, in addition to the effects of local factors on the oral mucosa. More research is needed to elucidate this problem.