Analysis of chromosome abnormalities in non-Hodgkin's lymphoma has stimulated a basic inquiry into the mechanisms of gene deregulation in human tumors. A growing literature has also correlated cytogenetic and molecular genetic features of lymphoma with patient prognosis and other clinical features of the disease. The goal of this report is to review those genetic abnormalities which are currently useful in the clinical management of patients with lymphoma, and to provide a conceptual framework for this growing literature.