Abstract: In five consecutive years，5319 serum samples were collected from different species of conventional, clean and specific pathogen free （SPF） laboratory animals in twenties facilities for the detection of viral antibodies. The results showed that the posi-tive rate of the antibody to Mousepox virus（MPV） was 3.2%（30/927），to Lymphocytic Choriomengitis virus （LCMV） was 0.3% （3/927） and 5.1% （21/914） in conventional mice and guinea pigs colonies, respectively. Antibody to Mouse Hepatitis virus（MHV） was 2.8% （26/914），and to Sendai virus was 2.0% （18/914） , 2.8%（4/141） and 33.3% （4/12） in clean mice，rats and guinea pigs colonies，respectively. Antibody to Reovirus type III（Reo-3） was found in SPF mice colonies kept in isolator with a positive rate of 1.6%（375/381）.

Key words: Virological quality , Conventional animals , Clean animals , Specific pathogen free animals