Among 23 Equidae in which various treatment or management regimens for salmonellosis were observed and evaluated, 9 horses were infected with Salmonella typhimurium and 8 with S anatum; an aged mule harbored S newport, and 1 isolant was not identified. Four dual sero-type infections occurred: 3 typhimurium/anatum and 1 anatum/newington. The results obtained with various antimicrobials in therapy of peracute, acute, and chronic infections were discouraging or questionable with regard to efficacy against salmonellae per se. The antimicrobial resistance patterns of the salmonellae and coliforms from the same fecal sample of the patient were determined. Salmonellae cultured from feces prior to, during, and following treatment with a variety of drugs were often sensitive to the antimicrobial administered during these periods. Drug sensitivity or resistance appeared to have little, if any, bearing on eliminating salmonellae from the feces or organs of infected Equidae.