The ability of selected anticoccidial drugs to inhibit the colonization of day-old male broiler chicks (Cornish Rocks) by Escherichia coli 0157:H7, strain 932 was examined. Chicks were challenged with 1.8 × 109 E. coli 0157:H7 on Day 1, and fed diets supplemented with three selected anticoccidial drugs; monensin, nicarbazin, or robenidine. The cecal and colon fecal contents of the chicks were removed on Day 7, 14, and 21 postinoculation and examined for the concentration of E. coli 0157: H7 per gram of contents. Monensin effectively reduced cecal and colon colonization of the chicks by E. coli 0157:H7. By Day 7, there were significant reductions in the bacterial population of the cecal contents of chicks receiving the monensinmedicated feed, and by Day 21 no E. coli 0157:H7 was recovered from the cecal and colon contents. The bacterial counts in the colon contents of the nicarbazinand robenidine-medicated and unmedicated chicks were significantly higher than the monensin-treated chicks. Bacterial populations in the colon contents were high only when there were high bacterial concentrations in the cecal contents.