Background and purpose: Giardia cyst and trophozoite have invariant morphologies, therefore, investigating aspects such as host specificity, transmission patterns and clinical behavior of the parasite in hosts requires molecular characterization of the parasites isolated from clinical samples. The aim of this study was to characterize giardiasis isolated from human fecal samples with symptomatic (with a history of chronic diarrhea) and asymptomatic giardiasis and investigating the correlation of parasite's assemblage with diarrhea. Materials and methods: Thirty one fecal samples containing Giardia cysts from individuals with symptomatic and asymptomatic giardiasis were used to characterize the parasites' genotype. Triose Phosphate Isomerase (TPI) gene was amplified by polymerase chain Reaction (PCR). Demographic information was recorded using a questionnaire and SPSS ver.16 and Fisher's exact test were applied to analyse the data. Results: PCR showed a higher frequency of Giardia duodenalis assemblage B compared with assemblage A (51.6 vs. 35.5). However, the frequency of Giardia duodenalis assemblage A in symptomatic giardiasis was significantly higher than that of the asymptomatic giardiasis (62.5 vs. 18.75). The Fisher's exact test revealed a significant correlation between Giardia doudenalis assemblage A and diarrhea (p<0.005). Conclusion: Usually, duodenalis assemblage A is accompanied by clinical symptoms such as diarrhea. However, duodenalis assemblage B is more prevalent among those with diarrhea
