Abstract： Objective To investigate effects of HBO on serum IL19 and 1L20 in the animal model of steroid - induced avascular osteonecrosis of femoral head. Methods Seventy-eight healthy New Zealand male rabbits were randomly divided into 8 groups: group N ( the control group),group M2,M4,M6 ( the model groups) and the HBO therapy groups (HBO group 2,HBO group 4,HBO group 6). The animal model of steroid - induced avascular osteonecrosis of femoral head was developed by injections of endotoxin and methylprednisolone. Rabbits in the HBO group 2,HBO group 4,HBO group 6 received HBO therapy 1 hour a day,and the duration of HBO treatment were 2 weeks ( HBO group 2),4 weeks ( HBO group 4) and 6 weeks ( HBO group 6) respectively. Contents of IL19,IL20 in serum were measured and histological changes in the femoral heads were observed as well. Results IL19 in group M0 increased significantly,when it was compared with that of group N(P＜0.05);IL19 in group M2 and M4 were much higher than those in group HBO group 2,HBO group 4 (P ＜0.05,P ＜ 0.01 ). IL20 in group M0 also increased significantly,when compared with that of group N( P ＜0.05 );IL20 in group M2 and M4 were much higher than those in HBO group 2 and HBO group 4 as well( P ＜ 0.01 ). Histological examination of the tissues of the femoral head revealed osteonecrosis and inflammatory cells in M2 and M4 groups,and lighter osteonecrosis together with less inflammatory cells in HBO group 2 and HBO group 4 groups than in M2,M4 groups. Conclusions Contents of IL19,IL20 elevated in the rabbit model of steroid-induced avascular osteonecrosis of femoral head. HBO therapy could inhibit release of IL19 and IL20,alleviate inflammatory response and decrease the extent of osteonecrosis.