Objective: This investigation was undertaken to evaluate the prevalence of intestinal parasitosis in patient addressed to the hospital of Oran and to identify parasites causing this infection. Design: The survey was made on 1042 individuals, external and hospitalized, having between one month and 80 years old, addressed te H.U.C. of Oran. For every patient, an analysis of stool sample was done including direct and complementary methods. Results: The prevalence is about 19,96%. Adultes (71,15%) are more parasited than children (28,84%). The sex ratio is equal to 1. It is essentially Protozoa parasitism with 95,7% and Helminth represent only 4,3%. The intestinal parasites founded are : Blastocystis hominis 47,17% Entamoeba coli 18,95%, Giardia intestinalis 15,32%, Endolimax nana 5,24%, Entamoeba histolytica 4 ,83%, Pseudolimax butschlii 4,43%, Enterobius vermicularis 2,82%, Cryptosporidium sp 0,4%, Ascaris lumbricoides 0,4% and Taenia saginata 0,4%. Statistically, it was no significant to the distribution of parasites species by sex. But according to age, it was significant for Giardia intestinalis which infects more children than adults, for Endolimax nana and Blastocystis hominis with the most infection of adults. Conclusion: The majority of parasites listed are not pathological. Their epidemiology is linked to faulty hygiene; this is why developing countries are the most concerned.