Three experiments were conducted to investigate the effects of concurrent infections of Salmonella typhimurium and Eimeria tenella on establishment of salmonella infection in chickens. There were four groups in all experiments: noninfected controls, birds infected with 50,000 E. tenella oocysts, birds infected with approximately 10(4) S. typhimurium, and birds infected with a combination of E. tenella S. typhimurium. In the first experiment with three identical trials of 80 birds each, chickens were infected with the organisms and necropsied 1, 3, 5, and 7 days later. Concurrent infections of coccidia and salmonella did not significantly enhance salmonella infection in terms of number of salmonella in the ceca and the number of positive birds for salmonella. In the second experiment, consisting of three replications of 80 chickens each, birds were exposed to salmonella on the day of coccidia exposure, 2, 4, or 6 days thereafter, and killed 1 day late. Salmonella in the ceca of coccidia-infected chickens did not increase significantly as compared with salmonella exposure alone. In the third experiment, with three replication of 60 birds each, chickens were exposed consecutively to salmonella 1 through 5 days and killed 7, 10, and 14 days after coccidia infection. There was a significant increase in number of salmonella in coccidia-infected ceca and number of chickens positive for salmonella in ceca or in liver when compared with those of salmonella infection alone.