The prevalence of intestinal parasites was studied as a function of socioeconomic conditions within La Plata, Argentina. Age, sex, and environmental factors were considered. Thus, from each of three areas within the city - the first a 'marginal' zone, the second a lower-income suburb, the third a middle-income urban district - 100,101, and 91 children up to 14 years old, respectively, were examined for intestinal parasites. Giardia lamblia was the most frequent species found. The respective prevalences of intestinal parasites overall (73, 54.4, and 35.1%), of polyparasitism (61.6, 27.2, and 12.5%), and of helminthic infection (32, 10.9, and 0.0%) were the highest within the population group having significantly inferior sanitary and environmental conditions. A positive statistical association between the prevalence of intestinal parasitosis and age was observed in all three of the neighborhoods. We also noted a correspondence between the frequency of such infections and school attendance in the two suburban districts. Management practices in accordance with the specific characteristics of an urban environmental and sociocultural ecosystem are thus important for the control of intestinal-parasite infection within municipal populations.