Abstract: In order to explore the mechanism of crocidolite injured lung,a in vitro model was formed with rabbit alveolar macrophage(AM)and human embryonic pulmonary fibroblasts(HEPF),the supernatant of AMs treated by crocidolite for 24 hours was prepared,and the proliferation of HEPF stimulated by supernatants of crocidolite treated AMs was measured by MTT color response method.At the same time,setting up positive control(SiO₂),negative control(TiO₂),normal control(AM) and blank control(B.Control).The results showed that the supernatants of crocidolite treated rabbit AM significantly stimulated the proliferation of HEPF with dose effect relationship(P<0.01).The net proliferative rate of HEPF in 100μg/ml crocidolite group reached 60 91%,higher than that of SiO₂ or TiO₂ group,and it was 3 48 times that of AM group.The higher dilution ratio was the supernatants of AM treated by 100μg/ml dusts,the less proliferation was HEPF,its dose effect relationship was significant(P<0.01),and there was stronger ability to stimulate the proliferation of HEPF at 1:2 dilution ratio of supernatants in different group than that of any other dilution ratio.It was suggested that there exist some bioactive factors in the supematants of crocidolite treated AM to stimulate the proliferation of HEPF.If the synthesis and secretion of those bioactive factors could be inhibited,it would make it possible providing the new way of prevention and treatment for asbestos related diseases.