Apart from ventilatory and bacteriologic aspects, understanding the pathomechanisms of inflammation in chronic sinusitis and nasal polyposis seems crucial for further success in disease treatment. New insights into inflammatory processes became recently possible by investigating the pattern of cytokines and chemokines as well as adhesion molecules in different acute and chronic sinus diseases. The proinflammatory cytokines interleukin (IL)-1 beta, IL-6 and especially the neutrophil-chemoattractant IL-8 play a dominant role in acute sinusitis, as was shown before for viral and allergic rhinitis. In contrast, IL-3 protein dominates the cytokine profile in chronic sinusitis, giving support to a variety of inflammatory cells. The most striking finding was the increased synthesis of IL-5 protein in bilateral nasal polyposis, whereas IL-5 was not found in controls or antrochoanal polyps. As this cytokine is known to enhance eosinophil activation and survival, our data point to IL-5 as a key protein in the pathomechanism of tissue eosinophilia in nasal polyposis. The investigation of cytokine patterns may furthermore help to differentiate between sinusitis subgroups, e.g. in the classification of sinus diseases.