We studied the stool samples of 151 school children in a district of the city of Portoviejo (Ecuador) in order to determine the prevalence and intensity of soil-transmitted helminthiasis (STH) It is estimated that more than 1 billion people in the world are infected by soil-transmitted helminths (STH) (Ascaris lumbricoides, Trichuris trichiura and hookworm) (Crompton 1999). These infections affect most frequently children in developing countries and are associated with poor growth, reduced physical activity and impaired learning ability (Stephenson et al. 1990, Nokes et al. 1992, Adams et al. 1994, Koroma et al. 1996, Stoltzfus et al. 1996. Infection can only be definitely controlled by improvement in sanitation and living conditions, but in the short term these measures can scarcely be implemented due to lack of resources.Periodic treatment of the endemic population with a broad spectrum anti-helminthic drug has been advocated as a cheap and effective mean of reducing the worm burden and its related morbidity (Montresor et al. 1998). The World Health Organization (WHO) recommends a baseline survey in schoolchildren to determine the prevalence and intensity of infections (Montresor et al. 1998 ment should then be given according to the results of the survey. The whole population should be treated in case of high prevalence and intensity, targeted treatment is preferred in case of high prevalence and low intensity, whilst case management is the option of choice in case of low prevalence and intensity.Aims of the study were to compare the intensity of the infections with anthropometric indexes and to identify the recommended measures to control STH infections in an urban district of Portoviejo (Ecuador), characterized by poor living conditions and insufficient sanitary standards. MATERIALS AND METHODS