Priority setting of scarce resources in healthcare is high on the agenda of most healthcare systems implying a need to develop robust foundations for making fair allocation decisions. One central factor for such decisions in needs-based systems, following both empirical studies and theoretical analyses, is severity. However, it has been noted that severity is an under-theorized concept. One such aspect is how severity should relate to temporality. There is a rich discussion on temporality and distributive justice, however, this discussion needs (...) to be adapted to the practical and ethical requirements of healthcare priority setting principles at mid-level. In this article, we analyze how temporal aspects should be taken into account when assessing severity as a modifier for cost-effectiveness. We argue that when assessing the severity of a condition, we have reason to look at complete conditions from a time-neutral perspective, meaning that we take the full affectable stretch of the condition into account without modifying severity as patients move through the temporal stretch and without discounting the future. We do not find support for taking the ‘shape’ of a condition into account per se, e.g. whether the severity has a declining or inclining curve, or that severity is intermittent rather than continuous. In order to take severity seriously, we argue that we have reason to apply a quantified approach where every difference in severity should impact on priority setting. In conclusion, we find that this approach is practically useful in actual priority setting. (shrink)