Privacy on the Internet has become one of the leading concerns for Internet users. These users are not wrong in their concerns if personally identifiable information is not protected and under their control. To minimize the collection of Internet users' personal information and help solve the problem of online privacy, a number of privacy-enhancing technologies have been developed. These so-called privacy-enhancing technologies still have usability issues in the user interfaces because Internet users do not have the choices required to monitor and control their personal data when released in online repositories. Current research shows a need exists to improve the overall usability of privacy-enhancing technology user interfaces. A properly designed privacy-enhancing technology user interface will give the Internet users confidence they can monitor and control all aspects of their personal data. Specific methods and criteria for assessing the usability of privacy-enhancing technology user interfaces either have not been developed or have not been widely published leading to the complexity of the user interfaces, which negatively affects the privacy and security of Internet users' personal data. This study focused on the development of a conceptual framework, which will provide a sound foundation for use in assessing the user interfaces of Web-based privacy-enhancing technologies for user-controlled e-privacy features. The study investigated the extent to which user testing and heuristic evaluation help identify the lack of user-controlled e-privacy features and usability problems in selected privacy-enhancing technology user interfaces. The outcome of this research was the development of a domain-specific heuristics checklist with criteria for the future evaluation of privacy-enhancing technologies' applications user interfaces. The results of the study show the domain-specific heuristics checklist generated more usability problems and a higher number of severe problems than the general heuristics. This suggests domain-specific heuristics can be used as a discount usability technique, which enforces the concept of usability that the heuristics are easy to use and learn. The domain-specific heuristics checklist should be of interest to privacy and security practitioners involved in the development of privacy-enhancing technologies' user interfaces. This research should supplement the literature on human-computer interaction, personal data protection, and privacy management.