Most of the literature on informed consent in pharmaceutical drug research works on the assumption that informed consent is something that is homogeneous and thus can be rendered procedurally universal. This may be justifiable to a certain extent owing to the fact these are all drug trials anyway. Nevertheless, in spite of this general similarity, we also know that the clinical drug development phases are characteristically different, and that phase IV is very different from the other phases because, owing to its postmarketing nature, it is much more varied in scope and in type. Thus, it is worthwhile looking into the ethical nuances relevant to the informed consent process in phase IV non-interventional drug research. We shall deal with the issues on the necessity of informed consent for this type of research and then discuss the possibilities for an opt-out system. We conclude that informed consent is necessary for non-interventional studies, and thus any form of waiving of rights of participants to informed consent must have a valid substantial justification. The distinct character of phase IV accounts for the difference in content of the informed consent document compared to that of earlier phases, and both opt-in and opt-out procedures are ethically justifiable as long as the participant's participation remains informed and voluntary.