B symptoms are a set of symptoms, namely fever, night sweats, and unintentional weight loss, that can be associated with both Hodgkin lymphoma and non-Hodgkin lymphoma. These symptoms are not specific to lymphomas, especially each one considered individually, and even as a trio they are not pathognomonic for lymphomas, but the presence of the trio is sensitive enough for lymphomas to warrant diagnostic investigation and differential diagnosis. The presence or absence of B symptoms has prognostic significance in lymphomas and is reflected in their staging.