() is a causative agent of peptic ulcer disease and plays an important role in the development of various other upper and lower gastrointestinal tract and systemic diseases; in addition to carcinogenesis and the development of mucosa-associated lymphoid tissue lymphoma, extragastric manifestations of are increasingly being unraveled. Therefore, prompt and accurate diagnosis is essential. Within this narrative review we present an overview of the current trend in the diagnosis of infection and its potential oncogenic sequelae, including gastric mucosa atrophy, intestinal metaplasia, dysplasia and gastric cancer. Signs of -related gastric cancer risk can be assessed by endoscopy using the Kyoto classification score. New technology, such as optical or digital chromoendoscopy, improves diagnostic accuracy and provides information regarding -related gastric preneoplastic and malignant lesions. In addition, a rapid urease test or histological examination should be performed, as these offer a high diagnostic sensitivity; both are also useful for the diagnosis of sequelae including gastric and colon neoplasms. Culture is necessary for resistance testing and detecting -related gastric dysbiosis involved in gastric oncogenesis. Likewise, molecular methods can be utilized for resistance testing and detecting -related gastric cancer development and progression. Noninvasive tests, such as the urea breath and stool antigen tests, can also be implemented; these are also suitable for monitoring eradication success and possibly for detecting -related gastric malignancy. Serological tests may help to exclude infection in specific populations and detect gastric and colon cancers. Finally, there are emerging potential diagnostic biomarkers for -related gastric cancer.