Background/aims: Perendoscopic prophylactic therapy is recommended in Forrest's II ulcers which are not bleeding ulcers with a visible vessel (IIa) or sentinel clot (IIb). The aim of this study was to clarify the use and outcome of perendoscopic prophylactic injection therapy in Forrest's II ulcers. Methods: Emergency endoscopy was performed on 38 patients with a history of upper-gastrointestinal bleeding (melena or hematemesis) within six hours and these with Forrest's II ulcers were included in the study. They were divided into two groups: Group 1 patients (n: 24) had prophylactic injection therapy performed with 1% aethoxysclerol and were then given medical treatment of 40 mg omeprazole intravenously twice daily and somatostatin infusion at a dose of 6 mg/day over three days. Group 2 patients (n:14) were given only medical treatment with the same agents and at the same doses but with no perendoscopic therapy. The two different treatment approaches were compared according to the rate of early rebleeding, duration of hospital stay, the number of endoscopic procedures, number of blood units transfused, improvement of local ulcer stigmata, number of deaths and need for surgery. Results: The groups were found to be similar according to initial endoscopic appearance of the ulcers (p>0.05). Early rebleeding (within 48 hours of inclusion in the study occurred in six (25%) Group 1 patients and two (14.2%) Group 2 patients (p<0.001). At follow-up endoscopy 48 hours later, nine (37.5%) patients in the group treated with perendoscopic prophylactic hemostasis and 10 (71.4%) patients in Group 2 showed improved local ulcer stigmata, having clear based ulcers with low rebleeding risk (Forrest's III) (p<0.001). The numbers of blood units transfused, duration hospital stay and number of endoscopic interventions were greater in Group 1 than in Group 2. There was no death or need for surgical intervention in either groups. Conclusion: According to these results, the indication for perendoscopic prophylactic injection monotherapy in nonbleeding ulcers with a high risk of rebleeding should be reviewed by large population based, prospective, randomized trials.