Objectve: To study the effects of luteinizing hormone-releasing hormone (LHRH) analogue nafarelin, estradiol(E2) and tamoxifen on the growth of BCaP-37 human breast cancer cell line in vitro. Methods: BCaP-37 human breast cancer cells (2.5×104/well) were cultured in DMEM with 5%no estradiol bovine serum. The number of BCaP-37 cell was counted after 96 h culture in following conditions respectively: (1) with nafarelin at 10-5-10-9mol/L, (2) with E2 at 10-7-10-10mol/L, (3) with nafarelin or tamoxifen at 10-6-10-8mol/L stimulated by 10-8mol/L E2, (4) with epidermal growth factor (EGF) at 10ng/ml or 50ng/ml, (5) with nafarelin between 10-5mol/L and 10-7mol/L influenced by EGF at 10ng/ml. Results: Nafarelin had no inhibitory effect on growth of BCaP-37 cell cultured at 10-5-10-9mol/L. At the concentrations between 10-6and 10-8mol/L, nafarelin or tamoxifen could antagonize the cell growth stimulated by E2 (10-8mol/L) respectively, and nafarelin had no effect on growth of BCaP-37 cell inhibited by EGF (10ng/ml). Conclusion: Nafarelin has no inhibitory effect on growth of BCaP-37 human breast cancer cell in vitro, but can antagonize the cell growth stimulated by estradiol.