In March 2005, CDC reported a multistate outbreak of Pseudomonas fluorescens bloodstream infections associated with use of syringes preloaded with heparin intravenous catheter flush. The heparin flush became contaminated during preparation by IV Flush, LLC (Rowlett, Texas). Thirty-six patients in four states were identified who had been exposed to the contaminated flush and subsequently experienced P. fluorescens bloodstream infection during December 2004-February 2005. Based on a recommendation by the Food and Drug Administration (FDA), IV Flush voluntarily recalled the preloaded syringes in late January; on January 31 and February 4, 2005, FDA issued nationwide alerts recommending that consumers and institutions stop using and return the preloaded syringes to IV Flush or the distributor (Pinnacle Medical Supply, Rowlett, Texas). Approximately 3 months after the product was recalled, patients in Michigan and South Dakota were identified with P. fluorescens bloodstream infections. As of April 2006, a total of 15 patients in Michigan and 13 in South Dakota had been identified with delayed onset P. fluorescens bloodstream infections, with occurrences ranging from 84 to 421 days after their last potential exposure to the contaminated flush. The patients all had indwelling central venous catheters and received treatment during October 2005-February 2006 at clinics known to have used the contaminated flush. This report describes the investigation of these cases, which determined that these were delayed onset cases of P. fluorescens bloodstream infection from a past exposure to contaminated flush, and provides recommendations for ongoing surveillance for delayed P. fluorescens bloodstream infections among similarly exposed patients.