Antral endocrine cells in four age groups of mice, namely prepubertal (1 month old), young (3 months old), ageing (12 months old) and senescent (24 months old), were detected by immunocytochemistry and quantified by computerized image analysis. A statistical difference was detected between the different age groups regarding the numbers of gastrin-, somatostatin-, and serotonin-immunoreactive cells. The number of gastrin-immunoreactive cells significantly increased between 1 and 12 months, whereas they became significantly fewer between 12 and 24 months. Somatostatin-immunoreactive cell number increased significantly in 1-, 12- and 24-month-old mice, compared with young mice (3 months old). The number of serotonin-immunoreactive cells also increased significantly in 1- and 12-month-old mice as compared with young mice. There was a statistical difference between different age-groups regarding the cell secretory index (CSI) of somatostatin- and gastrin-immunoreactive cells, the CSI of both somatostatin- and serotonin-immunoreactive cells increased significantly in 1-, 12-, and 24-month-old mice, compared with young mice. There was no statistical difference between the different age-groups regarding the CSI of gastrin-immunoreactive cells, nor between males and females regarding the number and CSI of all the endocrine cell types investigated. It is suggested that the large number of somatostatin-immunoreactive cells in ageing and senescent mice might have an impact on the gastric delay seen in the elderly. It was concluded also that the changes in the antral endocrine cells could be involved in the development of dysfunction of the gastrointestinal tract inherent in ageing, or could be secondary to structural and functional changes in the alimentary tract caused by ageing.