Background: The aim of this prospective study was to evaluate the interobserver agreement of stigmata of recent hemorrhage of bleeding peptic ulcers. Methods: Sixty-one consecutive adult patients were enrolled in the study and nine (three junior and six senior) endoscopists reviewed standardized video recordings of endoscopic examinations. Interobserver agreement was evaluated using the kappa (κ) index, intraclass correlation coefficient, and proportion of agreement. Observer bias and poorly trained observers were investigated. Results: Interobserver agreement was very good for oozing (κ = 0.68), good for clot (κ = 0.51), poor for spurting (κ = 0.29) and visible vessels (κ = 0.33), and excellent for the absence of stigmata (κ = 0.82). Observer bias sometimes occurred and the number of poorly trained observers was low. The κ indexes were significantly better in senior than in junior investigators: 0.48 ± 0.16 versus 0.37 ± 0.26, respectively, p < 0.05. The agreement between the in vivo evaluation and video tape recordings (intraobserver agreement) was good (κ = 0.60 ± 0.19). There was no training phenomenon between the first and the second half of the patient group. Conclusions: The endoscopic classification of bleeding ulcers might be simplified by limiting grading to a few classes. Special attention should be paid to the training of endoscopists.(Gastrointest Endosc 1997;46:27-32)