This article focuses on ethical issues faced in evaluation practice from the viewpoint of third generation of activity theory, which gives a constructive perspective on how contradictions can be a driving force behind interorganizational learning and development in multiactor networks. The problem field is firstly addressed through an illustration of the problematic position of evaluators in situations where cooperational relationships and professional networks are close. This perspective is then extended by an analysis of a reflection model designed to initiate discussion about the principles of evaluation. From an activity theoretical perspective, the ethical issues reflect contradictions, which can be a starting point for development, whether the actors can get oriented collectively in the analysis of a contradictory situation, and modelling, implementing and examination of a new solution. The analysed model for ethical reflection can be used, despite its limitations, as a heuristic framework for this kind of collaborative ethical reflection in a multivoiced network of people involved in the evaluation process. (Contains 6 figures and 3 notes.)