Large scale studies were performed to determine the prevalence of various intestinal helminth infections in urban and rural areas of Khuzestan Province, southwest Iran. A total of 16,361 stool samples from people in 105 villages and 14 small towns were examined by the formalin-ether concentration method. Ascaris, hookworms, Trichostrongylus, Trichuris, and Hymenolepis nana showed the highest prevalence. Hookworms and Trichostrongylus were twice as prevalent in rural than in urban areas; in contrast, H. nana was more prevalent in urban areas while the level of Ascaris infections was not significantly different. The intensity of Ascaris and hookworm infections, as estimated by the number of eggs/g of feces, was higher in rural than in urban areas.