In spite of frequent occurrence and long history of nasal polyps, their etiology and pathogenesis are still unknown. Various pathogenic mechanisms have been proposed by many inverstigators. Recent immunologic researches suggested that several cytokines could play important roles in the pathogenesis of allergic imflammatory disease. To investigate the expression of cytokine mRNAs in nasal polyps and the role of atopy in the pathogensis of nasal polyposis, we studied the expression of IL-4, IL-5, and INF-γ mRNAs using RT-PCR and Southern blot. Nasal polyp specimens were obtained from 7 patients with infectious rhinitis and 6 patients with perennial allergic rhinitis. Six normal nasal turbinate mucosa were also obtained from 6 volunteers. Most of RT-PCR products from 13 polyp specimens expressed a signal specific for each cytokine mRNA. However, such expression was less frequently obseved in normal turbinate mucosa specimens. Mean density ratios for each cytokine were similar in polyp specimens irrespective of presence of atopy. Mean density ratios of nasal polyp for each cytokine were higher than those of normal nasal mucosa. Mean density ratio of INF-γ was higher than that of IL-4, IL-5. The results of this study suggest that atopy itself may not contribute to the pathophysiology of nasal polyp.