Abstract: Objective :Giant cell tumor of bone(GCT) is an aggressive, potentially malignant tumor which occurs more frequently in Chinese people than in western people. The study attempts to elucidate the effect of Interferon alfa(IFN-a) on biological behavior and expression of basic fi-broblast growth factor (bFGF) and its receptor Bek in cultured cells of GCT in vitro, and to ex-plore an adjuvant therapy for preventing recurrence and pulmonary metastases of GCT. Methods :The fresh specimens of GCT in 15 cases were cultured and the biological behavior of cultured GCT cells were observed in vitro. The third generation cells of GCT incubated with different con-centration IFN-a in vitro were observed. The DNA content and apoptosis of the cells treated with IFN-a for 48 hours were analyzed by flow cytometry(FCM), and the expression of bFGF and Bek in these cells were tested by FCM and by cell enzyme-linked immunosorbent assay (C-ELISA). Results :The third generation cells of GCT treated for 10 to 12 hours with IFN-aat the concen-tration of more than 103IU/ml began to shrink and their growth were significantly inhibited andtheir numbers decreased. The cells treated for 48 hours with IFN-adeveloped apoptosis in a dose dependent fashion. IFN-aat the concentration of more than 100IU/m1 could significantly inhibited the expression of bFGF and Bek in the cells. The inhibitory effect is also a dose of IFN-ade-pendent model. Conclusion :IFN-ahas a significant antitumor effect on GCT cells in vitro and may be used as an adjuvant therapy for GCT in order to prevent or decrease the recurrence and metastases.