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Background: Nasal polyp (NP) is a benign mucosal mass located in both sinuses and nares which is mostly seen in association with cystic fibrosis, asthma or oversensitivity to aspirin. The prominent histological feature of NP is inflammatory cell infiltration with eosinophil predominance. Superantigens role in causing NP complications is already proven. Superantigens, which are mostly originated from Streptococci and Staphylococci, activate T cells strongly and increase the process of production and release of cytokines, and secretion of IgE from B cells, which in turn directly affects proinflammatory cells such as eosinophils, both in their tissues infiltration and functions. Methods: The samples are collected from patients referring to ENT clinic in Rasoul Akram training Hospital in Tehran after thorough clinical and paraclinical examinations. For control group the samples collected from patients undergoing rhinoplasty. All the samples kept frozen and sent to immunology lab. The DNA of the excised tissues extracted and amplified by using the superantigens specific primers and PCR product detected by gel electrophoresis. The date analyzed by using mean and SD and X2 analytical tools. Results: Fifteen healthy individuals, 25 patients with rhinosinusitis and 24 with polyposis entered this trial. Group A Streptococcus toxin detection was significantly more frequent in those with nasal polyp and rhinosinusitis compared to healthy individuals (P=0.001 and 0.005, respectively), but the results were almost the same for those with nasal polyp and rhinosinusitis (P=0.4). Conclusion: Streptococci may play an important role in induction or clinical exacerbation of polyposis and group A Streptococcus pyogenes exotoxin (SPEs) with superantigenic effects may have a crucial role in etiology and pathogenesis of polyps with or without rhinosinusitis. It is postulated that, T cells polyclonal activation by SPEs may cause recruitment of inflammatory cells in nasal mucosa. These inflammatory cells include IgE producing B cells laeding to allergic and inflammatory reactions in NP. [ABSTRACT FROM AUTHOR]