Spectrum analysis of the radiofrequency echo signals obtained from ultrasonically scanning the prostate may provide information capable of distinguishing cancerous from noncancerous tissue. In American men, prostate cancer is the highest‐incidence cancer and the second‐highest cancer killer. It is diagnosed using ultrasonically guided biopsies, which are limited by the low sensitivity and specificity of the guidance method. Spectrum analysis of the echo signals uses information that is discarded by conventional ultrasound imaging technology. The inclusion of this information shows differences between the ultrasound‐scattering properties of cancerous and noncancerous prostate tissues. Spectrum analysis of ultrasonic echoes provides parameter values that can be related to scattering properties of tissue and can be compared to database parameter value ranges associated with cancerous and noncancerous tissues. Images can be generated to display parameter values, scatterer properties, or most likely tissue type. Results to date suggest that these differences may be sufficient to improve biopsy guidance significantly and therefore to improve the efficacy of biopsy‐based diagnosis of prostate cancer. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 11–25, 1997