A sensitive micro EIA utilizing antigen or antibody dotted onto nitrocellulose filters (Dot-ELISA, Dot-blot) has been developed for laboratory diagnosis of hemorrhagic fever with the renal syndrome (HFRS) by detecting the virus specific IgM and IgG in the sera of HFRS patients and the antigen in crude lung suspensions of wild rodents. Measurements of specific IgM and IgG in paired HFRS sera collected during the first month of the disease showed clear-cut seroconversion and 100% correlation with the results of immunofluorescent test. The results of antigen detection in lung suspensions of 605 wild rodents trapped in various regions of Russia were identical to standard ELISA results. This rapid and inexpensive test may be useful in early serologic diagnosis of HFRS and in field serological and epizootological studies.