Asymptomatic eosinophilia is a common finding in returning travelers and immigrants from parasite-endemic areas. We present a 49-year-old man from Guyana who immigrated to the United States 4 years prior to examination. He had persistent asymptomatic eosinophilia, and multiple stool examinations were negative for ova and parasites. Although the list of parasitic diseases associated with eosinophilia is extensive, the differential diagnosis of asymptomatic eosinophilia with negative stool evaluations is rather limited. We discuss herein elements of the clinical history and examination essential for evaluating eosinophilia in patients at risk of parasitic diseases and present a simple algorithm to guide diagnostic testing. Despite the importance of repeated stool examinations for the presence of ova and parasites, in practice this test is not sensitive. Serologic testing for chronic parasitic infections is often necessary. Most cases without a definitive diagnosis can be conservatively managed with serial monitoring or empirically treated with antihelminthic therapy, but patients with an absolute eosinophil count of more than 3000/μL or more than 1500/μL for more than 6 months are at risk of end organ damage and should be referred for specialized parasitic and/or hematology consultation.