Turkey poults obtained from a commercial source were vaccinated with a water-in-mineral oil vaccine consisting of one part complete Freund's adjuvant and one part of a watery suspension of heat-inactivated Bordetella (B.) bronchiseptica-like organisms. Birds of group A received one dose of vaccine at 4 days of age, group B received one vaccination at 4 days of age and a second vaccination at 27 days of age. The vaccine was injected subcutaneously at the base of the neck. A third group (C) of poults served as a non-vaccinated control and a fourth group (D) as a negative control. At the 41st day of age birds of groups A, B and C were challenged by infraorbital inoculation of viable virulent organisms. Eight days later all birds of groups A, B, C and D were killed and examined for pathological changes and samples from the respiratory tract were cultured for B. bronchiseptica-like organisms. The vaccine produced a reversible tissue reaction of an acceptable degree at the site of inoculation in approximately 30% of the birds after the first vaccination and in most of the birds after the second vaccination. The results of these experiments show that one vaccination at 4 days of age does not give a full protection. However, after two vaccinations full protection could be observed. The vaccine was also effective in increasing the clearance rate of B. bronchiseptica-like organisms from the trachea. Results of cultural examination 8 days post-challenge revealed the presence of viable organisms in 100% of the non-vaccinated birds but only in 50% of the poults immunised once and in only 25% of the birds immunised twice with the oil adjuvant vaccine. Both vaccination and challenge induced the production of agglutinating antibodies against the heat labile antigen of the Bordetella strains used.