Abstract： Objective To investigate the expression of nucleolin in osteosarcoma and its clinical significance.Methods The expression of nucleolin was evaluated by immunohistochemistry in paraffin-em bedded tissues from 35 cases of osteosarcoma and 15 cases of osteochondroma.Results Among the osteo sarcoma cases, 8.6％ were negative for nucleolin, 20％ weakly positive, 34.3％ moderate positive, 37.1％ strong positive.The positive rate of nucleolin in osteochondroma was 40％, 46.7％, 13.3％, 0％, respectively.The nucleolin expression showed significant difference in the osteosarcoma and osteochondroma (P ＜0.01).Among the conventional ostcosarcoma cases, 6.9％ were negative for nucleolin, 13.8％ weakly positive, 34.5％ moderate positive, 44.8％ strong positive.The positive rate of nucleolin in paros teal osteochondroma was 16.7％, 50％, 33.3％, 0％, respectively.The nucleolin expression showed re markable correlation with pathological and genetical classification (P ＜ 0.05).The positive rate of nucleo 1in in osteoblastic osteochondroma was 5.9％, 5.9％, 29.4％, 58.8％, while in chondroblastic osteochon droma 0％, 33.3％, 33.3％, 33.3％ and 16.7％, 16.7％, 50％, 16.7％ in fibroblastic osteochondro ma, respectively.The positive expressions of nucleolin were almost the same in each subtype of osteosarco ma (P ＞ 0.05).Conclusions The nucleolin expression had correlation with property of tumors in bone, and the positive expressions of nucleolin had correlation with pathological and genetic classification of osteo