[en] The cervical esophagus of 22 adult mongrel dogs was irradiated in a schedule of 300 rad per fraction, 3 times a week, to either a total dose of 3000 or 6000 rad. 2 weeks after completion of irradiation, 1 cm of the esophagus in the irradiation field was resected, and Olsen type 1 layered anastomosis was performed. All of the animals were sacrificed for comparison with a non-irradiated group 2 weeks after surgery. Failure of the sutures occurred in 1 of 18 non-irradiated dogs (5.6%), 1 of 9 dogs given 3000 rad (11.1%), with no significant difference, and 5 of 7 given 6000 rad (71.4%), with a significant difference from the other two groups. Irradiation of 3000 or 6000 rad provoked decrease of the interstitial content of hydroxyproline to 70% or 85%, respectively. Although an increasing tendency was observed 2 weeks after anastomosis, the values of the irradiated groups were lower than those of the non-irradiated group. Histopathologically, a strong reaction, chiefly edema, was noted in the submucosal layer. (Chiba, N.)