A serological surveillance was carried out to detect antibody against influenza A virus in chicken sera. A total of 8, 850 field samples were collected from 47 prefectures in Japan. Initially, all the sera were screened by agar gel immunodiffusion and those sera showing positive reaction were investigated for haemagglutination-inhibition (HI) and neuraminidase-inhibition antibodies against influenza viruses. Only 6 samples had antibodies; 4 sera had antibodies against human subtype H1N1 virus; with HI activity against strain A/PR/34; three sera had strong HI activity to strain A/Tottori/4/87, which by haemagglutination test is closely related to A/Yamagata/120/86. The remaining two chicken sera had antibodies against avian subtypes H10N4 and H3N6 viruses respectively.