The present experimental study was designed to assess whether administration the agonistic analog of gonadotrophinreleasing hormone (aLH-RH) has any effect on development of N-nitroso-N-methylurea (NMU)-induced tumors,and evaluate the vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) expression,during the acute and chronic treatment with goserelin.N-Nitrosomethylurea was given to 45 days, Wistar female rats on two occasions.The groups were 1) controls, n=10 and 2) treated, n=30.Then, the last group was subdivided for (a) acute and (o) chronic study.They were treated with aLH-RH (Goserelin, Astra-Zeneca, UK).The rVEGF and rEGFR assay were performed in plasma and tumors homogenate by enzyme linked immune-absorbent assay (ELISA, R&D Systems, and by Amersham Biotech, Barcelona, Spain).Post 2nd administration of NMU, mammary cancer was detected in eighty percent of rats, on days 65 and with incidence of 1.5 tumors per rat.The mean control plasmatic value of VEGF was higher in rats with NMU tumors than in healthy control rats.During acute treatment with goserelin, in the time course in plasma was compared basal values to 60 minutes was increased significantly.