Four hundred and fifty subjects were included in a study of the prevalence of soil-transmitted nematodes in Ujung Pandang, South-Sulawesi, Indonesia. Trichuriasis was the most prevalent infection (93.3%), followed by ascariasis (80.2%) and hookworm infection (19.5%). Among 156 subjects who were given 500 mg of mebendazole in a single dose, treatment resulted in cure rates of 93.4%, 77.6%, and 91.1%, and average egg-count reduction rates of 99.0%, 92.8%, and 98.3%, for ascariasis, trichuriasis, and hookworm infections, respectively. Mebendazole appeared to be equally effective against necatoriasis and ancylostomiasis. The drug was well tolerated and almost no side effects were observed. Single dose mebendazole treatment appears to be relatively inexpensive, convenient, and effective in mass treatment for the control of intestinal nematode infections, especially in highly infected communities.