Methods for evaluating the quality of watermarked objects are detailed in this chapter. It will provide an overview of subjective and objective methods usable in order to judge the influence of watermark embedding on the quality of audio tracks. The problem associated with the quality evaluation of watermarked audio data will be presented. This is followed by a presentation of subjective evaluation standards used in testing the transparency of marked audio tracks as well as the evaluation of marked items with intermediate quality. Since subjective listening tests are expensive and dependent on many not easily controllable parameters, objective quality measurement methods are discussed in section Objective Evaluation Standards. Section Implementation of a Quality Evaluation presents the whole process of testing the quality taking into account the methods discussed in this chapter. Special emphasis is devoted to a detailed description of the test setup, item selection and the practical limitations. The last section summarizes the chapter.