This book represents the results obtained over a period of several years of research in the field of ultrasonic tissue characterization. Mainly focused on the development of a computer-aided diagnostic system for the detection of prostate cancer and on the discussion of the results of the underlying clinical study, the work may also be of help to scientists working in the field of ultrasonic tissue characterization and focusing on other organs. Eight different groups of tissue parameters and features applicable for tissue characterization and typically used by the tissue characterizing community have been evaluated and described in detail. This discussion may be a valuable source for scientists working in the same field or approaching the field of tissue characterization. In addition to the statistical tools necessary for the evaluation of tissue parameters and for the classification of biological tissue, a modern classifier, the so-called adaptive network-based fuzzy inference system, is introduced and described to a degree that will facilitate application and usage of the classifier by the reader who intends to establish a higher order classification system. Though most parts of the system have been designed for prostate cancer detection, studies on the classification of coronary plaques, on the differentiation of blood and vessel wall in intravascular ultrasound, on the staging of deep venous thrombosis and on the monitoring of thermal ablation therapy have recently proved the reliability of the approach described in this work.