The efficacy of chicken egg yolk homotypic antibodies specific for outer membrane proteins (OMP), lipopolysaccharide (LPS) or flagella (Fla) in controlling experimental salmonellosis in mice was investigated. Mice challenged orally with 2 x 10(9) c.f.u. of Salmonella enteritidis or 2 x 10(7) c.f.u. of S. typhimurium were orally treated with 0.2 ml anti-OMP, -LPS or -Fla yolk antibody three times a day for three consecutive days. In mice challenged with S. enteritidis, antibody treatment resulted in a survival rate of 80%, 47% and 60% using OMP, LPS or Fla specific antibodies respectively, in contrast to only 20% in control mice. In the S. typhimurium trial, survival rate was 40%, 30% and 20% using OMP, LPS or Fla specific antibodies respectively in contrast to 0% in control mice. In vitro adhesion of S. enteritidis and S. typhimurium to HeLa cells was significantly reduced by anti-OMP, -LPS, and -Fla homotypic antibodies. Results suggest that egg yolk antibodies specific for Salmonella OMP, LPS, and Fla may protect mice from experimental salmonellosis when passively administered orally. Of these antibodies, anti-OMP exhibited the highest level of protection in vivo and in vitro.