Outer membrane protein isolated from Salmonella gallinarum was examined at different concentrations with or without a mineral-oil adjuvant for its immunogenicity and protection against live challenge. A formalin-killed whole-cell bacterin of the same organism was used for comparison. The results suggested that membrane proteins from S. gallinarum give better protection than formalin-killed whole-cell bacterin. Addition of an oil adjuvant to the protein appeared to increase the efficiency of the vaccine. When protein was given to chickens at 400 micrograms/100 g of live body weight, it produced 100% protection against oral challenge with S. gallinarum.