OBJECTIVES: I. Determine the frequency of chromosome 3, 11, and 21 aberrations in peripheral blood lymphocytes (PBL) specifically associated with acute myelogenous leukemia in patients with adult or pediatric Hodgkin's disease treated with radiotherapy and/or chemotherapy. II. Determine the frequency of these aberrations in patients with pediatric central nervous system tumors treated with radiotherapy and/or chemotherapy. III. Determine the glutathione-S-transferase allotype, associated with human toxicological response to carcinogen exposure, for these patients. IV. Determine the frequency of t(14;18) gene rearrangement, associated with deregulation of the bcl-2 proto-oncogene in non-Hodgkin's lymphoma, in PBL of these patients.