Serum renin-angiotensin-aldosterone(RAA)levels were determined on169 occations in 96 cases of hemorrhagic fever with renal syndrome(HFRS).Theresults reveal that RAA system levels rise in vaviable degrees in different stages ofHFRS,the highest value being in the hypotensive and oliguric stages and thenormal value,in the polyuric and convalescent stages.The elevation range iscorrelated with the severity of the disease.Being closely related to the decrease ofblood volume before the bypotensive stage and to the“tubuloglomerular feedback”mechanism after the oliguric stage,the activation of RAA system may be one ofthe contributing factors of the acute renal failure in HFRS.