In order to determine the challenge dose of pigeon paramyxovirus type 1 (PPMV-1) inactivated vaccine (S-1 strain). The virus titer of PPMV-1 E5 allantoic fluid (Chuansha strain) was determined using SPF chicken embryos in this research. After inoculating 30-day-old and 120-day-old pigeons with low-HI antibody against PPMV-1 (HI antibody < or =2) with different doses of PPMV-1 (Chuansha strain), the clinical symptoms and histopathological lesions of the challenged pigeons were examined. The results showed that the minimal lethal dose (MLD) of PPMV-1 (Chuansha strain) was 102.5 ELD50, so we determined that 10(5.5) ELD50, which was 1000 times the MLD, could be taken as the challenge dose in the vaccine efficacy test for PPMV-1 inactivated vaccine (S-1 strain).