The relation between allergy and cancer has been investigated within an integrated series of case-control studies of digestive tract and laryngeal neoplasms conducted in Italy since the early 1990s. These included 598 patients with incident, histologically confirmed cancer of the oral cavity and pharynx, 304 of the oesophagus, 1225 of the colon, 728 of the rectum, 460 of the larynx and 4999 controls, selected among patients admitted to the same network of hospitals as cases for acute, non-neoplastic diseases. Inverse associations with history of allergy were found for all cancer sites examined (odds ratio=0.44 for oral cavity and pharynx, 0.80 for oesophagus, 0.76 for colon, 0.54 for rectum and 0.33 for larynx). The associations were consistent in strata of age and sex, and when subjects with a first diagnosis of allergy 5 or more years before cancer diagnosis or hospital admission were considered. The present study therefore provides further evidence for a possible protective effect of prior history of allergy on cancer risk.