Authors used double-labeled immunocytochemistry for studying the localization and distribution of hemorrha-gic fever with renal syndrome virus (HFRSV) antigen in the peripheral blood lymphocyte subpopulations in HFRS patients and the quantitative changes of these subpopulations. It was found that HFRSV might infect dif-ferent subpopulations of lymphocytes. The infection rate of B cells (31.3%) was significantly higher than that of Tcells (8.5%), and the infection rate of CD8;subpopulation (10.5%) was significantly higher than that of