Unlike the small intestine and colon where -radiation-induced apoptosis has previously been well characterised, the response of murine gastric epithelium to -radiation has not been investigated in detail. Apoptosis was therefore assessed on a cell positional in gastric antral and corpus glands from adult male mice following -radiation. Maximum numbers of apoptotic cells were observed in both antrum and corpus at 48h and at radiation doses greater than 12Gy. However the number of apoptotic cells observed in the gastric epithelium was much lower than observed in the small intestine or colon after similar doses of radiation. Haematoxylin and eosin, caspase 3 immunohistochemistry and TUNEL detected similar numbers and cell positional distributions of apoptotic cells, hence H and E was used for subsequent studies. The highest numbers of apoptotic cells were observed at cell positions 5-6 in the antrum and cell positions 15-18 in the corpus. These distributions coincided with the distributions of PCNA-labelled proliferating cells, but not with the distributions of H⁺/K⁺/ATPase-labelled parietal cells or TFF2-labelled mucous neck cells. Decreased numbers of apoptotic gastric epithelial cells were observed in p53-null, bak-null and bax-null mice compared with wild-type counterparts 6h and 48h after 12Gy -radiation. Significantly increased numbers of apoptotic gastric epithelial cells were observed in bcl-2-null mice compared with wild-type littermates 6h after 12Gy -radiation. Radiation therefore induces apoptosis in the proliferative zone of mouse gastric epithelium. This response is regulated by the expression of p53, bak, bax and bcl-2.