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Background and purpose: Giardiasis is a major diarrheal disease and the major symptoms include diarrhea, bloating, abdominal cramps, weight loss, and abdominal pain. In developing countries, some patients can carry giardia parasites without experiencing any symptoms and some genotypes are believed to be responsible for that. The aim of this study was the genotyping of giardia duodenalis in asymptomatic patients. Materials and methods: A total of 320 stool samples was collected from people attending Baharestan health centers in Tehran, Iran and investigated for giardia cyst by microscopic method. Positive samples were stored in Potassium dichromate 2.5% and 4ºC. DNA extraction was performed using CTAB method and genotyping was carried out by PCR-RFLP on β-giardin gene. Results: Among the samples, 25 were positive (7.8%). All patients suffering from giardiasis were asymptomatic and the appearance and color of samples were normal and brown, respectively. Four samples were found in women (16%) and 21 in men (84%). The results of RFLP on these samples revealed that 16 samples (64%) had infections with assemblage A and 9 samples (36%) were assemblage B. The phylogenetic tree revealed sub-assemblage AII, BIII, and BIV to be present in Baharestan. Conclusion: The most common genotype of Giardia duodenalis is assemblage A in asymptomatic people in Baharestan, Iran. Identification of AII, BIII, and BIV genotypes in this area indicates the possibility of anthroponotic and anthropozoonotic transmission cycles.