The aim of this study was to evaluate the effectiveness of an educational program carried out in 1993. The intervention took place after the first external quality assessment in coproparasitology, conducted in 77 laboratories of Havana City. Centers receiving training were compared with the those that did not, and better results were obtained in the municipalities of 10 de Octubre, Plaza, and Cerro, as well as in all laboratories that sent people to training. Better diagnosis was found for the helminths Trichuris trichiura, Taenia sp., and Fasciola hepatica as well for the protozoans Blastocystis hominis and Endolimax nana in the laboratories that received training. The laboratories that received training had significantly higher scores than those which did not. The results point to the effectiveness of the educational intervention. We recommend external quality assessment in coproparasitology as well as on-going, mandatory technical education, held at regular intervals. Such measures should assure steady improvement in diagnosis of intestinal parasites by the health services network.