Parasitic infections are an important public health issue due to their high prevalence and widespread incidence. In Brazil there are no data on the performance of clinical laboratories regarding fecal examinations. The purpose of this study was, therefore, to assess the performance of clinical laboratories in Curitiba and its Metropolitan Region, Paraná state, on the diagnosis of intestinal parasitic infections. Samples were sent to laboratories in three semipermanent preparations on glass slides for microscopy analysis and three samples in diluent solution. The forwarded samples contained ten different parasite species and 22 possible diagnoses. The laboratories were scored very good, good, average or below average according to a predetermined standard. None of the assessed laboratories scored very good regarding the diagnosis of intestinal parasitic infections, 21.1% of laboratories scored good, 15.8% average and 63.2% below average. There were 22% false positives and 24.4% false negative results. The diagnosis of Ascaris lumbricoides eggs was least mistaken. The most common diagnostic failures were in the identification of hookworm larvae, Iodamoeba bütschlli cysts and Fasciola hepatica eggs. The poor performance of laboratories in parasitological diagnosis demonstratedthat parasitology laboratories are neglected and professional training is not up to standard.