Background and Study Aims: A few studies have been published on cancers missed at previous endoscopy, but detailed analyses of the causes for failure were lac king. The aims of our study were to determine the incidence of and causes for fa ilure to detect oesophageal and gastric cancers after referral of patients to a surgical endoscopy unit. Patients and Methods: Out of a consecutive series of 30 5 patients diagnosed with oesophageal and gastric cancers, we retrospectively id entified patients who had undergone an endoscopy within 3 years before the diagn osis. The timing of previous endoscopies, indications for endoscopy, endoscopic findings and the number of biopsy specimens taken were recorded. Missed diagnose s were categorized as either definitely or possibly missed and the reasons for f ailure were documented. Results: Of the 305 patients, 30 (9.8%) had undergone a minimum of one endoscopy within the previous 3 years, 20 (67%) of these within the previous 1 year. Sinister symptoms were present at the time of previous end oscopies in 75%of patients with oesophageal cancer (n=16) and in 57.2 %of pati ents with gastric cancer (n=14). In 56%of the patients with oesophageal cancers the initial diagnosis was oesophagitis or benign stricture; in 71.4%of the pat ients with gastric cancers the initial diagnosis was gastritis, ulcer or “suspi cious lesion“. Among those patients with a definitely missed diagnosis (7.2%), endoscopist errors accounted for the majority of failures (73%) and the remaind er were due to pathologist errors (27%). Conclusions: Missed cancers were a fre quent finding in patients with oesophageal and gastric cancer who had undergone previous endoscopy, and errors by the endoscopists accounted for the majority of missed lesions. This study emphasizes the importance of identifying signs of ea rly cancers and of having a low threshold for performing multiple biopsies of an y suspicious-looking lesion. Background and Study Aims: A few studies have been published on cancers missed at previous endoscopy, but detailed analyzes of the causes for failure were lac king. The aims of our study were to determine the incidence of and causes for fa ilure to detect oesophageal and Patients and Methods: Out of a consecutive series of 30 5 patients diagnosed with oesophageal and gastric cancers, we retrospectively id entified patients who had undergone an endoscopy within 3 years before the diagnosis. The timing of previous endoscopies, indications for endoscopy, endoscopic findings and the number of biopsy specimens were recorded. Missed diagnosed s were categorized as either definitely or likely missed and the reasons for f ailure were documented. Results: Of the 305 patients, 30 (9.8%) had undergone a minimum of one endoscopy within the previous 3 years, 20 (67%) of these within the previous 1 year. Sinister sympto ms were present at the time of previous end oscopies in 75% of patients with oesophageal cancer (n = 16) and in 57.2% of pati ents with gastric cancer (n = 14). In 56% of the patients with oesophageal cancers the initial diagnosis was oesophagitis or benign stricture; in 71.4% of the patients with gastric cancers the initial diagnosis was gastritis, ulcer or ”suspi cious lesion". Among those patients with a definitely missed diagnosis (7.2%), endoscopist errors accounted for the Most of failures (73%) and the remaind er were due to pathologist errors (27%). Conclusions: Missed cancers were a fre quent finding in patients with oesophageal and gastric cancer who had undergone previous endoscopy, and errors by the endoscopists accounted for the majority emphasizes the importance of identifying signs of e r r cancers and of having a low threshold for performing multiple biopsies of an y suspicious-looking lesion.