Oral inoculations of sporulated oocysts of Eimeria acervulina, E. necatrix, E. brunetti, E. tenella, or none were given to five groups of 4-wk-old chicks. Fecal samples were taken at 1, 3, 5, 6, 7, 8, 11, 14, and 21 days postinoculation and total fecal aerobe, total fecal anaerobe, fecal lactobacilli, and fecal coliform concentrations were enumerated. Fecal aerobe concentrations increased 10-fold during the period from 3 to 8 days postinoculation. Fecal anaerobe concentrations had small increases from 3 to 6 days. Fecal lactobacilli concentrations increased with E. necatrix and E. brunetti infections but decreased with E. tenella infections. Fecal coliform concentrations increased most with the duodenal infections and increased less with posterior tract infections.