Chromosomal aberrations are characteristic and specific events; the detection of chromosomal abnormalities often provides information on diagnosis and prognosis of disease. Some patients with large-cell anaplastic lymphoma (Ki 1 lymphoma) have the translocation t(2;5) (p23; q35), involving a possible growth-regulating tyrosine kinase. We found this translocation in 11 patients with Hodgkin's disease of nodular sclerosis and mixed-cellularity types. This finding has implications for the understanding of the relation between large-cell anaplastic lymphoma and Hodgkin's disease, diseases with morphological and immunophenotypical similarities. Study of this translocation may help understanding of the origins of cancer and cancer growth. It also allows a more precise definition of Hodgkin's disease and may be used as an indicator for clonality--which has long been sought.