Although prostaglandins (PGs), especially PGE2 and PGF2α, are thought to be associated with inflammation, there have been no papers dealing with the synthesis of PGE2 and PGF2α in human tonsillar lymphocytes. The features of PG synthesis in lymphocytes were investigated by incubating cells with radiolabelled precursors. Synthesis of PGE2 was greater than that of PGF2α in tonsillar lymphocytes. PGE2 was the predominant product in the tonsillar lymphocytes of the recent infection group. There was no significant differene between T and B lymphocytes in the ratio of PGE2 and PGF2α formed. A significant increase in PGE2 formed with bradykinin was found in the tonsillar hypertrophy group. The possible role of PGs in the pathogenesis and mechanism of releasing free fatty acid PG precursors from cell membranes was discus