Studies were performed on the relationship between hard cured gastric ulcers and fungi in rats. Experimental gastric ulcers were prepared by the use of the Clamping-Cortisone method. Rats with experimental gastric ulcers were divided into 3 groups, A, B and C. Group A was neither administered drugs nor fungi. Group B was given Candida albicans. Group C was dosed chlorhexidine. The results were as follows: 1. Experimental gastric ulcers with fungi in their bottom were found in 4 rats out of 13 belonging to group B. 2. The defection of fungi on the crate surface of the experimental gastric ulcers revealed that positive results were obtained in all cases of group A or B and in 3 cases out of 11 of group C. As to the species of the fungi, in group a Torulopsis famata, in group B Candida albicans and in group C. Torulopsis famata were identified respectively. 3. The normal fungous flora in the intact stomachs of experimental animals was identified as Torulopsis famata. 4. The fungous form in the bottom of experimental gastric ulcers was yeastlike in the cases that were sacrificed 3 weeks later making ulcers. In case the heading of experimental gastric ulcers was protracted, there were seen mycerial fungi increasing in quantity. 5. The crater surface of the gastric ulcers of group B where fungi grew abundantly was dirty histlogically and the recovery of gastric ulcers was delaye l. The scar formation of gastric ulcers of group B was weaker than group A and C. These results apparently indicate that the course of the gastric ulcers with fungi in their bottom will be delayed in group B. 6. The recovery of experimental gastric ulcers in group C was most remarkable among 3 groups. It may be posible that the application of chlorhexidine as the gastric ulcer agent will contribute to the purification of the surface of gastric ulcers and promote the healing of them.