The prevalence of fluoroquinolone-resistant enteric bacteria in agricultural and municipal waste streams was investigated by surveying for resistant Escherichia coli in samples collected from nine locations in the United States and one location in Mexico. None of the 102 isolates that were tested were resistant to either ciprofloxacin or ofloxacin. Microcosm studies using a clinical (ciprofloxacin resistant) Pseudomonas aeruginosa isolate suggest that the resistance phenotype is stable over multiple generations in the absence of selective antibiotic pressure. Copyright (C) Elsevier Science Ltd.