The aim of this study was to determine the type of phospholipase A2 (PLA2) in nasal fluid and to demonstrate its cellular origin. The concentration of group II PLA2 was high (591.5 micrograms/l) in nasal fluid compared with serum level (10.8 micrograms/l) and the fluid of paranasal sinuses (10.6 micrograms/l). Methacholine stimulated nasal fluid contained only small amounts (19.1 micrograms/l) of group II PLA2 when the flow of tear fluid through the nasolacrimal duct was obstructed. Occasional glands secreting group II PLA2 were found in nasal and paranasal mucosa by immunohistochemistry. Lysozyme was found in the majority of mucosal glands. It was concluded that nasal and paranasal mucosal glands contain group II PLA2. In nasal fluid, however, PLA2 is mainly derived from tear fluid.