The authors considered the incidence of second neoplasms among 1,672 oesophageal cancers diagnosed between 1974 and 2004 in the Cancer Registries of the Swiss Cantons of Vaud and Neuchatel, and followed-up to 2004. A total of 141 second neoplasms were observed versus 38.5 expected, corresponding to a standardized incidence ratio (SIR) of 3.7 (95% confidence interval: 3.1-4.3). The SIRs were statistically significant for cancers of the oral cavity and pharynx (57.3), larynx (24.3), lung (6.6) and intestines (2.6). The SIRs were higher in subjects diagnosed below age 50 and in the first year after diagnosis. The SIR of upper digestive and respiratory tract neoplasms was higher for oesophageal cancers diagnosed in the upper (87.5) and middle (68.1), as compared with the lower third (19.4). There was no rise of second oral, pharyngeal and laryngeal cancer with advancing age, and their incidence tended indeed to decline from 100/1,000 at age 40-49 to 25/1,000 at age 70-79. There was no tendency to rise with age in the incidence of first oesophageal cancer in subjects who subsequently developed another upper digestive or respiratory tract neoplasm. The excess risks of upper digestive and respiratory tract neoplasms are attributable to increased diagnosis and registration of second neoplasms following a diagnosis of oesophageal cancer, as well as to heavy tobacco and alcohol consumption in oesophageal cancer cases. The absence of rise in incidence with age is also compatible with the existence of a subset of the population of susceptible individuals. [Ed.]