BACKGROUND: Adenocarcinoma limited to the esophagus (ACE) arises in Barrett's esophagus (BE). The incidence of ACE is therefore restricted to this BE subpopulation, whose size is unknown and which is for 95% unidentified. AIMS: To determine the age- and gender-specific incidence rates of ACE, limited to the BE subpopulation, within a defined geographical area and to compare them with those of squamous cell carcinoma of the esophagus (SCC), which can affect the entire population. METHODS: The age- and gender-specific incidence rates for ACE and adenocarcinoma of the cardia (AGC) were calculated after an expert panel classified 87% of all cases of adenocarcinoma of the esophagus reported to the Danish Cancer Registry over a 6-yr period as ACE or AGC. RESULTS: The age-specific incidence rates of ACE for males rose from 0.09/105 (30-34 yr) to 14.14/105 (80-84 yr), falling to 7.2/105 (85+ yr), for females from 0.19/105 (45-49 yr) to 2.79/105 (80-84 yr), falling to 2.43/105 (85+ yr) and yielding a gender ratio of 5.9:1; AGC demonstrated a similar pattern and a gender ratio of 4.26:1. However, the incidence rates of SCC continued rising after the age of 80 yr, with a gender ratio of 2.46:1. CONCLUSIONS: The continuing rise in the SCC incidence rates in the elderly demonstrated that the unexpected decline and fall in the incidence rates of ACE over the age of 80 yr did not result from underdiagnosis but were most probably caused by a declining prevalence rate of BE, restricting the elderly BE subpopulation at risk of developing ACE.