Field cancerization was first described in 1953 as histologically altered mucosa surrounding tumours removed from the upper gastro-intestinal tract. Over the years the definition has changed to include an area which is clinically occult but has multifocal preneoplastic changes, showing genetic mutations and which precedes the development of second primary tumours and local recurrences. Field cancerization has been described in the oropharynx, oesophagus, stomach, lung, colon, anus, cervix, bladder and skin. Various molecular techniques have been developed to look for genetic mutations and clonality in areas of field change. These studies have highlighted the need for early detection and treatment in order to prevent the development of tumours and local recurrences. In this article we examine the concept of field cancerization and treatments available to manage field change.