The major aims of the study are to characterize childhood NHL with respect to chromosomal abnormalities and immunologic phenotype, and to relate the findings of these studies to etiologic factors derived from case/control interviews and EBV viral studies. The interviews will focus on immune-related disorders in the family of the patient, and unusual or chronic antigenic exposures of the patient. This is an extension to a study that is expected to reach its initial goals of total patient accrual, but will fall short with respect to accrual of the important subgroup of patients who have tumor tissue available for study. The specific aims for the next two years are to include an additional 80 patients into this subgroup. Incident cases of NHL, enrolled on therapeutic studies of the Children's Cancer Study Group, will be eligible. Biopsy material from these children will be used for cytogenetic analyses, immunopathology studies, histopathology, and EBV serology. Serum will be frozen for future use. The mothers of cases, and a matched control group selected by random digit dialling, will be interviewed by telephone to provide data on familial associations, particularly of immune-related conditions such as autoimmune disease and allergy, and on environmental exposures of the child and parents. It is hoped that this study will provide a clearer understanding of the interrelations of viruses, chromosomal abnormalities, and genetic and acquired immune function disturbances in childhood NHL.