A collection of readily reproducible molecular techniques to better understand, classify, and treat lymphoma. Among the highlights are methods to use immunoglobulin gene rearrangements as markers of clonality, to exploit patterns of somatic mutation in the variable regions to indicate at which stage transformation occurred, and to apply gene arrays to the question of biological heterogeneity in morphologically similar diseases. Research methodologies that are highly likely to become routine practice in the future, such as DNA microarray and immunoglobulin V-gene rearrangements, and measurement of minimal disease, are included. There are also molecular techniques for providing for producing novel therapeutics, such as a DNA vaccine with patient-specific sequences derived from the lymphoma in question.