Hantaviral antibodies were detected in the sera from Apodemus (A.) agrarius and A. peninsulae captured in Ningxia province, China by several different serological diagnostic methods. A total of 409 sera from rodent and insectivore species were collected in 1999 and examined by indirect immunofluorescent antibody assay (IFA). Among them, 19 of 191 (9.9%) sera of A. agrarius and 1 of 13 (7.7%) sera of A. peninsulae were positive for hantaviral antibodies. The other species (Rattus norvegicus, Mus musculus, Cricetulus triton, and Sorex cylindricauda) were negative. The reaction pattern of positive serum was characterized as scattered and granular virus antigens in the cytoplasm of hantavirus infected Vero E6 cells. Some of the A. agrarius sera positive for hantavirus were further examined by Western blotting (WB), enzyme-linked immunosorbent assay (ELISA), and the focus reduction neutralization test FRNT By WB, positive sera showed the same specific reaction pattern of baculovirus-expressed recombinant hantaviral nucleocapsid protein, as shown in hantavirus-immune serum. By ELISA, IFA-positive sera showed significantly higher optical densities (around 1.0) than the negative A. agrarius sera. Hantaan type hantavirus was neutralized with the positive sera. These results suggest that A. agrarius have hantavirus infection and may play a role as a reservoir animal for hantavirus in Ningxia Hui Autonomous Province, China.