Platelet activating factor (PAF; 10 micrograms) was injected in the peritoneal cavity of rats in the absence or presence of the PAF antagonist BN-52021 (5 mg/kg). Thirty min later, the peritoneal cavity was washed with 3 ml of saline, the fluid was collected and the concentrations of selected eicosanoids were measured using novel enzyme immunoassays. PAF increased by 2.9, 2.8 and 1.7 fold the levels of thromboxane B2, prostaglandin E2 and leukotriene B4 respectively in the peritoneal fluid. The stimulatory effects of PAF was reduced by 42, 51, and 86% for thromboxane B2, prostaglandin E2 and leukotriene B4 respectively by the specific PAF antagonist. These results confirm the presence of specific PAF receptors in tissues and/or cells of rat peritoneal cavity and underline the complex interactions between PAF and eicosanoids.