Traveller's diarrhea in patients staying principally at resorts is usually a self-limited illness caused by enterotoxigenic Escherichia coli. Persisting symptoms are often due to non-infectious causes, such as transient lactose intolerance or dietary change. Parasitic infestation -- helminthic and amebic -- is much less common and a diligent search for such parasites isn't warranted in many individuals. A single sample will usually suffice. In people who are likely to have a parasitic infection, however -- i.e. prolonged stay in rural/endemic areas, consumption of contaminated foods/water, eosinophilia -- it's recommended that three separate stool specimens for microscopic examination be examined in order to maximize the chances of detection. KL