Lymphomas, cancers orginating in a type of white blood cell known as a lymphocyte, account for five percent of cancers in the United States. This issue not only reviews imaging of the various types of lymphoma but also provides a background on clinical aspects and staging criteria. Positron emission tomography has had a great impact on the diagnosis of lymphoma, and several articles on PET and other molecular imaging modalities are included. The issue also contains articles on cross-sectional imaging.