Low molecular weight, heparin(LMWH)possesses multiple nonanticoagulant properties.In the present study, we observed its anti-airway allergic inflammatory effects by bronchoalveolar lavage in guinea pigs.Guinea pigs were sensitized by repeatedly inhaling aerosolized ovalbumin.LMWH(400u/l, 800u/l), dexamethasone(1.2mg/l)or vehicle(normal saline)was inhaled for 7 days.Then the animals were sacrificed under anesthesia and then lavaged with ice-cold Hank’s buffer immediately;bronchoalveolar lavage fluid(BALF)was prepared 24h afterr the animals were challenged by antigen exposure.The effects of LMWH on total cell counts, absolute eosinophil counts and cell catalogues in BALF were studied;effects on the activity of eosinophil peroxidase(EPO)and the contents of histamine and eosinophil cationic protein(ECP)in BALF supernatant were detected.Our results showed that compared with the vehicle group, LMWH at 400u/l and 800u/l could significantly reduce total cell counts, absolute eosinophil counts and percentage of eosinophils in BALF(P<0.05 and P<0.01, respectively);LMWH at 800u/l markedly inhibited the activity of EPO in BALF supernatant(P<0.05);LMWH at 400u/l and 800u/l remarkably reduced the content of histamine in BALF supernatant(P<0.05 and P<0.01, respectively), LMWH at 800u/l decreased the content of ECP(P<0.05)significantly.It suggested that LMWH exerted anti-airway allergic inflammatory action by inhibiting infiltration of inflammatory cells and reducing release of inflammatory mediators, as well as antagonizing their activities, and that LMWH could be developed as a potential anti-bronchial asthmatic drug.