An experience with 65 dogs subjected to gastric freezing for 30 minutes with inflow temperatures of -18.6°, -20° or -29.4° C. (Groups I, II or III) indicated a definite incidence of post-freeze gastric ulcer for each group. Superficial erosions also occurred, but most did not seem to bleed or cause serious concern. The incidence and size of post-freezing gastric ulceration in Groups I and II was influenced favorably by the prior intravenous infusion of low molecular weight dextran at doses of 2 gm./kg. body weight. Mortality from post-freeze ulcers was lowered from 7 deaths (30.4 per cent) in control Groups I and II, to 1 death (4.5 per cent) in the corresponding dextran groups. The limit of effectiveness of this agent was approached at inflows of -29° C. in Group III in which 5 of 6 dogs developed post-freeze ulcers, two of them dying from perforation. The secretory depression attending freezing of Heidenhain pouches was not abrogated by systemic use of low molecular weight dextran. The clinical use of low molecular weight dextran in man during gastric freezing may offer promise of decreasing the 2 per cent observed incidence of the post-freeze gastric ulcer.