The interest in the prostaglandin (PG) synthesis by animal cells today grows steadily because of the difficulties in obtaining them by any other way. Murine peritoneal macrophages can under certain conditions synthesize large amounts of PGs. The effect of well-known nonsteroidal anti-inflammatory drug ibuprofen on PG synthesis by the cells using a high-performance liquid chromatography (HPLC) method with fluorescence detection of 4-bromomethyl-7-methoxy-coumarin (BrMMC) derivatives was studied. In our case, the main metabolites were PGE(2) and PGF(2a). The PG synthesis activation effect was shown by ibuprofen concentrations in the 10(-10)-10(-14)M range with the maximum effect at the 10(-12)M. In this case, the ibuprofen effect was comparable in value with the effect of the well-known cell PG synthesis activator-calcium ionophore A(23187). Although the exact mechanism of such an effect is not clear at the moment, at low concentration, ibuprofen itself is able to activiate PG synthesis in murine peritoneal macrophages.