The purpose of this paper is to describe and discuss the approach for the tasks of ethical peer review and ethical guidance which was adopted in the project Friendly Rest Room for Elderly (FRR). Two aspects of user involvement were of special concern for the ethical reviewers: first of all, the target group consisted of potentially frail (or, vulnerable) users, and, second of all, problems relating to toileting and personal hygiene are considered taboo subjects in most regions of Europe. A mixture of a normative and empirical approach to ethics was adopted for guiding the project's user involvement. Ethical guidelines and principles relevant for the FRR context were identified and empirical work was performed to study their implementation. As methods for data collection, participant observation of prototype trials and interviews with users and developers were applied. In addition, the ethical peer reviewers participated closely in the drafting of information materials for users and in planning and designing of the user trials. In designing the user tests, much attention was paid to efforts to lessen the taboo effect faced by participants who were asked in the presence of a research team to talk about their toileting routines and difficulties. In this paper, the normative and empirical work performed by the ethical review team in the FRR project is described and key observations are discussed. In conclusion, the main lessons learned in the continuous process of ethical peer review in the FRR project are presented.