This paper describes the "Privacy-Enhancing Technology Users' Self-Estimation Scale (PET-USES)", a questionnaire that enables users to evaluate PET user interfaces for their overall usability and to measure six different PET aspects. The PET-USES is intended to be used during usability testing and evaluation of PET user interfaces. The focus of the PET-USES is the subjective experience of the user rather than the intrinsic PET functionality of the application being tested. Although the test has been developed within the PrimeLife project to test the usability of PETs developed therein, the test is constructed in such a fashion that it should be applicable to a wide variety of PETs. The objective of this paper is to outline the creation and the background of the PET-USES questionnaire and invite the usability community not only to use the test, but also to contribute to the further development of the PET-USES.