Inactivated FMD vaccine is weakly immunogenic and multiple vaccinations at four-month intervals are necessary for the prevention of the disease. Our results revealed in cyclophosphamide treated animals, the antibody titers remained protecting up to 35 weeks post vaccination, while in non treated group, the animals became susceptible to infection 19 weeks post vaccination. So, it is possible t increase the duration of neutralizing antibodies in serum when a low single dose of cycliphosphamide is administered four days before vaccination with aluminium hydroxide-saponin FMD vaccine and this will increase the intervals between vaccinations and decrease the commercialization costs of vaccination programs.