The purpose of the work was to assess the vaccine, elaborated by the authors, under laboratory and field conditions. For the production there was used the La Sota strain which have been employed for many years for the production a vaccine against Newcastle disease. The strain after propagation on chick embryos was inactivated with formalin (0.1%). Mineral oil was used as an adjuvant. The value of the vaccine was determined indirectly, i.e. on the basis of HI antibody production. The experiment under laboratory condition was carried out on 30 pigeons, aged 1—2 months, and on eight chickens, aged 3 weeks, and under field conditions on 60 000 pigeons in some regions of Poland. The assessment of the vaccine under close controlled conditions was done on 20 pigeons, and on 10 pigeons there were performed comparative examinations using two vaccines produced by foreign manufactures. It was found that the vaccine induced in pigeons following two injections 4 weeks apart a good immune response comparable with that after using vaccines of this type made by other manufactures. The highest level of HI antibody after two injections in pigeons was 6.9 log₂ and decreased slowly reachingat month 9 the level 2.9 log₂. In chickens a mean geometric HI titre (log₂) after two weeks was 7.2 and after the second injection 8.4. In vaccinated pigeons no side effects were observed; only in a small perecentage of birds there occurred transient changes in the from of swelling at the site of injection.