Abstract: A method of determining the severity of prostatic cancer includes measuring the level of amplification of the HER-2/neu gene in a sample of prostate tissue by fluorescence in-situ hybridization and comparing the measured level of amplification of the HER-2/neu gene in the sample with the level of HER-2/neu gene in normal prostate tissue. A method for determining treatment for a patient afflicted with prostate cancer includes determining whether the number of copies of HER-2/neu gene in prostate cells from the patient exceeds four by using fluorescence in-situ hybridization and aggressively treating such patient having prostate cells with five or more copies of the HER-2/neu gene.