Cotton fever is usually a benign febrile, leukocytic syndrome of unknown etiology seen in intravenous narcotic abusers. Cotton and cotton plants are heavily colonized with Enterobacter agglomerans. We report a case of cotton fever associated with E agglomerans in which the organism was first isolated from the patient's blood and secondarily from cotton that he had used to filter heroin. Enterobacter agglomerans is with most probability the causal agent of cotton fever. Patients presenting with the classic history should have blood cultures performed and should be started on a regimen of empiric antibiotic therapy.