The Newcastle disease virus (NDV) was solubilized with 10% w/v Tween 80 and inactivated with 0.05% v/v formalin. The average molecular mass of the released antigenic subunits was 307 kD. The tested vaccine was prepared in the form of a water-in-oil-in-water emulsion (WOWE) vaccine. The oil-to-aqueous ratio was 1:2. The solubilized NDV was administered alone or built in a tetravalent WOWE vaccine. A dose of the monovalent vaccine containing an equivalent of 44.7 microliters of detergent-treated NDV-allantoic fluid (NDV-AF) was sufficient for the complete protection of the commercially available chickens vaccinated at the age of 5 wk and challenged 7 wk later. The anti-NDV-free chickens, vaccinated at 4 wk of age and challenged 2 wk postvaccination, were 100% and 73% protected by a vaccinal dose containing 178.6 and 89.3 microliters of detergent-treated NDV-AF, respectively. Commercially available light pullets, primary vaccinated with live lentogenic NDV vaccine, generated a protective level of NDV antibodies after revaccination with WOWE vaccine containing 89.3 microliters of detergent treated NDV-AF. Laying hens were revaccinated under field conditions at the beginning of the laying cycle by the tetravalent vaccine. A vaccinal dose/bird containing 11.2 microliters of detergent-treated NDV-AF elicited a long-lasting high level of NDV neutralizing antibodies.