Of a total of 3,366 cases of malignant lymphoma in China reviewed histopathologically, T-cell lymphomas accounted for an average of 26.1% among all non-Hodgkin's lymphomas. However, the proportion of lymphomas of T-cell lineage varied in different parts of China, with the highest proportion (30-40%) along the east coast. Immunologic typing of 41 non-Hodgkin's lymphomas by the avidin-biotin-peroxidase complex technique revealed similar patterns. When serum antibodies to human T-cell leukemia virus were assayed in 462 normal men and 103 monkeys, 2-5% of the men and 8.4-15% of the monkeys were positive for antibodies to this virus.