Carthamus tinctorius L. is a traditional Chinese medicine with the effect of promoting blood circulation and removing blood stasis. HSYA (hydroxysafflor yellow A) is the main effective component of Carthamus tinctorius L. In order to study the inhibitory effects of HSYA against PMN (polymorphonuclear) activation induced by LPS (lipopolysaccharide), rabbit PMN adhesion potency which was activated by LPS through colorimetry method was observed. Cellular free calcium concentration was determined by fluorescence spectrophotometry. RT-PCR was applied to study the effect of HSYA on PMN TNF-alpha and IL-6 mRNA expression; The inhibition of HSYA on NF-kappaB activation was monitored with immunofluorescence. The results showed that after treated with HSYA, the increase of adhesion potency (HSYA dose 1.01 x 10(-4) mol x L(-1)), free calcium concentration (HSYA dose 3.1 x 10(-5) mol x L(-1)), TNF-alpha and IL-6 mRNA expression elevation (HSYA dose 5.2 x 10(-1) mol x L(-1)) induced by LPS were inhibited. HSYA can inhibit NF-kappaB p65 subgroup nuclear translocation (HSYA dose 5.2 x 10(-5) mol x L(-1)). It is suggested that HSYA is effective in PMN activation induced by LPS.