Abstract: Infection of LCM virus is very common and often persistent and recessive in squirrel and laboratory mice colonies. The titer of virus in blood is very high and antibody to LCM can be detected in virus-carrier mice at the same time. Wild mice is a vector of the disease. In resent years, the movement of killing wild mice has been launched everywhere in our country. Only in Beijing, 400 thousands of wild mice were killed in 1986. For the purpose of rising the quality of laboratory mice, ELISA, IFA, EIA and IAHA were employed in serological checking and comparison of four methods was performed in our laboratory. It is of great advantage to adding sample, recording OD. value automatically and to judging results easily by using ELISA. A hundred of samples can be checked by two persons in half a day. IFA is a more specific than EIA and IAHA The results showed that ELISA is the most sensitivite. Since 1982, we have detected 2824 of mi e, the positive rate of serum antibody is the highest in 1985 (13.91％). In 20 provinces and cites in which mice were sampled, we found that infection occurs in 13 provinces and cities (65％). The positive rate is the higest in Shandong province (90％), secondly, Henan province (75％) Beijing (65％), Anhui and Zhejiang provinces (50％) in dividually.