RESEARCH market enrofloxacin for use in poultry in the United States. Our studies had several limitations. The retrospective case-comparison study did not assess exposures among travelers and therefore cannot assess the possibility that the travelers may have acquired ciprofloxacin-resistant Campylobacter from eating poultry or other foods while traveling. Routine surveillance for antimicrobial suscepti- bility among Campylobacter did not start until 1997, and therefore we cannot identify national trends in antimicro- bial resistance from 1991 to 1996. Other limitations are evident in NARMS Campylobacter surveillance, including the use of sentinel clinical laboratories in some states and some variation in the isolation procedures. However, these limitations are not likely to be associated with an increased (or decreased) likelihood of selecting antimicrobial-resist- ant isolates for submission to NARMS since the antimicro- bial resistance pattern of the isolates were not known when the isolates were selected. Lastly, because NARMS Campylobacter surveillance was not nationwide and resistance may differ regionally, generalization to the U.S. population should be done with caution. In summary, we describe the emergence over the last decade of fluoroquinolone-resistant Campylobacter infec- tions in the United States. As of 1997, more than half of such infections were domestically acquired. In 1999, fluo- roquinolone-resistant Campylobacter organisms were present on a substantial fraction of chickens sold at super- markets in three widely separated locations in the United States. Continuing national surveillance of human infec- tions and prospective national monitoring of the frequency of contamination of poultry at retail would provide useful ongoing information. Clinicians should include macrolides, such as azithromycin, as a first-line treatment of severe Campylobacter infections. Acknowledgments We thank Allen Ries, Felecia Hardnett, Robert Hoekstra, Jocelyn Rocourt, and Charlotte Sumner for their assistance with this manuscript. Funds for this study came from the Emerging Infections Program, Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, and from state funds to support public health surveillance activities. Dr. Gupta is a former EIS fellow of the Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, and is now on the faculty at Johns Hopkins University, Division of Infectious Diseases. 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