An external quality assessment in coproparasitology was carried out in 77 laboratories from Havana City. A questionnaire and ten plastic vials with different intestinal parasites in a small nylon bag, duly sealed, were sent to each laboratory. Answers were collected during the 72 hours after delivery. Results were analyzed by means of a computer program. The majority of the laboratories (70%) passed the test; the municipalities with the worst scores in the province were Lisa, Marianao, and Habana del Este. Better results were obtained among technologists working only in parasitology than those who were also performing other laboratory work, and better averages were observed in hospitals than in polyclinics. The best identified intestinal protozoan was Giardia lamblia and the worst identified was Blastocystis hominis (with a 61% mistake rate), followed by Endolimax nana (24.6%), and Entamoeba histolytica (22%). Among helminths, the best identified was Trichuris trichiura (9.2% mistake rate) and the highest percentage of incorrect diagnoses was for Taenia sp. and Fasciola hepatica (both with 66.2%). Taking into account these results, we feel it is necessary to provide training in parasitology among these laboratories.