Although the etiology of nasal polyposis is still not revealed, insights in the pathogenesis have largely expanded over the last years. Usually nasal polyps occur in adults, are bilateral and are characterized by a manifest tissue eosinophilia. Deposition of plasma-proteins (albumin), potentially driven by subepithelial eosinophilic inflammation, seems to be an early and key pathogenic factor in the development of nasal polyps. Accumulation and activation of eosinophils is favoured by low TGF-beta1 concentrations and overproduction of IL-5 and eotaxin. In nasal polyps high IgE concentrations are measured. Our findings indicate that this IgE is produced locally. Total IgE and the expression of specific IgE is unrelated to skin prick tests, but correlates with the degree of eosinophilia. In addition, we demonstrated the organisation of secondary lymphoid tissue in nasal polyps and a polyclonal hyper-immunoglobulinemia E, associated with the presence of IgE specific to Staph. aureus enterotoxins (SAE), colonization with Staph. aureus and increased eosinophilic inflammation in a relevant subgroup of NP patients (about 50%). In about half of the nasal polyps we thus find a local immune response against SAE. SAE can hereby act as conventional allergens, triggering T- en B-cells to produce sIgE against SAE. On the other hand, SAE can also act as superantigens and induce polyclonal B-cell activation and hyper-immunoglobulinemia. In addition, the presence of IgE antibodies to SAEs seems to be associated with the severity of asthma and nasal polyposis disease. Nasal and oral corticosteroids are currently the standard treatment for NP. This treatment however, is not always sufficient and oral corticosteroids have several side effects. Often surgery is required, which in turn is not free of complications and recurrencies. Increasing insights in the pathophysiology of NP opens perspectives for new pharmacological treatment options, with eosinophilic inflammation, IgE and Staph. aureus as potential targets.