Purpose: The etiology of sinonasal polyps is sometimes obscure. This study was undertaken to evaluate the potential role of arachidonic acid metabolites (AAm) on recurrent polyposis. Materials and Methods: Tissue production of prostaglandin E2 (PGE2), 6-ketoprostaglandin F1-alpha (PGl 2), thromboxane A2 (TxA2), and leukotriene C4 (LTC4) by nasal mucosa was determined by radioimmunoassay in 27 patients with sinonasal polyposis (SNp) and in 10 volunteers. Results: The group of patients with SNp with the evidence of recurrences in postoperative period (Group 1) showed significantly lower PGE2 concentrations than group of patients with SNp recurrences (Group 2). The differences in concentrations of PGI2 in mentioned groups were insignificant. In comparison with other groups, a group of patients who underwent surgery several times for SNp (Group 4) had a higher mean TxA2 concentration. The LTC4 concentrations were the highest in groups of patients where SNp recurrences were observed. When the incidence of polyposis recurrences (within 18 months after surgery) was correlated with the level of LTC4 production at the time of surgery, the rate of recurrence was significantly higher in patients with increased LTC4 level than in those with normal LTC4 levels. Conclusions: LTC4 might have a prognostic value. The possible role of AAm in occurrence of SNp is apparent and suggests possible role for medical intervention.