Abstract: Coxsackie A 16 viruses were isolated from herpetic liquid and blood of 11 in 16 children with HFMD during 1985 in the district of Changchun. The titers of neutralizing anti-bodies and specific IgG to the virus in 12 sera of 16 sick children during convalescent phase were four times higher than that of the acute phase, the specific IgM to the virus in 12 sera of acute phase was all positive by immunoenzymatic method after SPA absorption, while only one of 20 healthy children gave positive result. It indicates that the method measuring specific IgM can be served for the early diagnosis of HFMD.