Background: One of the common gastro-intestinal parasites worldwide is Blastocystis. Diverse subtypes are employed to detect this microscopic parasite but there is not enough information on the issue if these su-btypes may exhibit diverse clinical symptoms or not. This research aimed at the evaluation of the clinical symptoms of the disease like itching and gastro-intestinal symptoms in various subtypes as well as in Blastocystis co-infection with other parasites. Methods: We extracted DNA from the fecal specimens of the cases that had been referred to the Center for Tropical Diseases in Verona-Italy. Moreover, real-time PCR (RT PCR) was employed to identify the available parasitic infections and nested PCR to detect the subtypes. Then, SPSS was used to analyze data. Results: Any significant relationship did not exist between the subtypes and clinical symptoms. In addition, co-infection did not significantly related to the disease symptoms and a number of parasites. The small statistical population may influence such results. Conclusion: Further investigations must be conducted for determining the effects of Blastocystis sub-types and their co-infection on the disease symptoms.