The oral vaccination against Fowlpox was investigated via drinking water containing the F132-c strain of Fowlpox virus to be effective even though the vaccine virus-titer was 10(4) TCID50/dose each time. When the virus-titer of the F132-c strain was 10(4-5) TCID50/dose per single drinking water vaccination, 90% or more of chickens were not protected, however, they were protected when vaccinated twice via drinking water. A weak immune response occurred by a slight infection after the first vaccination, and due to memory cells, a booster could work well after the second vaccination. These results suggest the possibility of reducing both the amount of virus required for a vaccine via drinking water and the labor cost in the field.