The recognition of specific oesophageal infections and the distinction between gastro-oesophageal reflux disease and rarer forms of oesophagitis are key tasks for gastrointestinal pathologists reading mucosal biopsies. Infections can involve the oesophagus either primarily or as part of a wider process. This chapter highlights their features, discussing in detail the common infections including herpes simplex, cytomegalovirus, and Candida, and summarises the features of the rarer ones. A few additional types of oesophagitis have emerged recently, including eosinophilic oesophagitis and lymphocytic oesophagitis. This chapter reviews the recent literature and will discuss the controversies surrounding some of these new entities. There is an emphasis on the need for correlation between clinical/endoscopic information and microscopic appearances, and there is discussion of supplementary special studies including immunohistochemistry where relevant.