Chemical or reactive gastritis is commonly induced by endogenous substances such as bile and pancreas secretions, but can it also be caused by exogenous noxious substances, including acetylsalicylic acid, nonsteroidal anti-inflammatory drugs, chemotherapeutics, and alcohol. The histopathological patterns are similar, involving epithelial damage extending up to erosions with consecutive regenerative hyperplasia and damage to capillaries, with edema, hemorrhage, and proliferation of smooth muscles. As cellular infiltrates are minimal or lacking, some authors have proposed the term "gastropathy" instead of the term chemical or reactive gastritis as proposed by the updated Sydney classification. This contribution describes the different patterns and grades and discusses their pathogenesis. Mixed forms of chemical/reactive gastritis and other forms of gastritis are also described, for example, that from Helicobacter.