The aim of this systematic review was to critically evaluate all epidemiological studies reporting an association between Camellia sinensis consumption, in the form of green tea, and a reduced risk of gastrointestinal cancer. Epidemiological studies of C. sinensis consumption in relation to gastrointestinal cancer or preneoplastic lesions were identified through computerised literature searches using the following databases: Medline (Pubmed), Embase, Amed, CISCOM, Phytobase and Cochrane Library. Only epidemiological studies indicating the type of tea (green tea from C. sinensis) and the site of either cancer or precancerous lesions (stomach or intestine) were included. No language restrictions were imposed. Twenty-one epidemiological investigations met the inclusion/exclusion criteria. These studies seemed to suggest a protective effect of C. sinensis on adenomatous polyps and chronic atrophic gastritis formations. By contrast, there was no clear epidemiological evidence to support the suggestion that green tea plays a role in the prevention of stomach and intestinal cancer.