The majority of malaria cases diagnosed in the United States are imported, usually by persons who travel to countries where malaria is endemic. However, small outbreaks of locally acquired mosquito-transmitted malaria continue to occur. Despite certification of malaria eradication in the United States in 1970, 11 outbreaks involving 20 cases of probable locally acquired mosquito-transmitted malaria have been reported to CDC since 1992, including two reported in July 1996 from Palm Beach County, Florida (Palm Beach County Health Department, unpublished data, 1998). This report describes the investigation of seven cases of locally acquired Plasmodium vivax malaria that occurred in Palm Beach County during July-August 2003. In addition to considering malaria in the differential diagnosis for febrile patients with a history of travel to malarious areas, health-care providers also should consider malaria as a possible cause of fever among patients who have not traveled but are experiencing alternating fevers, rigors, and sweats with no obvious cause.