Abstract: Plasma TXB2 and 6-K-PGF_1α were measured by radioimmunoassay in 50 patients wish SLE and 38 healthy persons.The result showed that the 6-K-PGFIa levels of SLE patients were lower than those of controls.The TXB2 values of severe group (SG) and active group (AG) were significantly increased when compered with those of mild group (MG),stable group (STG) and control group (CG).The K/T (6-K-PGF_1α/TXB2) ratios of all SLE groups < CG.The K/T ratio correlates with the severity of the disease.The results suggest that the determination of both TXB2 and 6-K-PGF_1α is helpful for the evaluation of the therapeutic effect and prognosis in SLE patients.