Intestinal parasites in white-faced capuchin monkeys Cebus capucinus Primates: Cebidae) inhabiting a protected area in the Limón province of Northeastern Costa Rica. Deforestation of tropical forests is threatening monkey biodiversity and their health status, dependent of an ecologically undisturbed area. To asses this relationship, we analyzed parasite occurrence in their intestines. The study was conducted at the Estación Biológica La Suerte (EBLS), Limón, Costa Rica. The group of white-faced capuchin monkeys (Cebus capucinus) was observed between March and December of 2006. A total of 75 feces samples were obtained. Once a sample was collected, the eaten plant type was identified to family and species level, and feces were processed in the laboratory to determine parasite incidence. Results showed that Moraceae was the most represented family in the samples. Among parasites, Strongyloides spp. and Acanthocephala were the most common. Positive prevalence of parasites was found similar and independent of sex and age of capuchin individuals. Microsporids were mainly reported in feces associated with Piperaceae. A low presence of these parasites was found in samples associated with Myrtaceae, with possible anti-parasite active components. The occurrence of parasites was relatively high in EBLS, when compared to other regions in Costa Rica. The higher occurrence of parasites observed in capuchins at EBLS may be due to the fact that this rain forest is surrounded by areas affected by human activities. We suggest the promotion of research in neotropical primates parasitology, for a better comprehension of the parasite-host relationship, and in a long term, being able to understand the ecosystems where they coexist, and consequently, preserve the biodiversity of the whole region.