In this article, the vitality of premature infants will be described and discussed. Vitality was one of the main factors in a grounded theory study in which the aim was to generate knowledge concerning the ethical decision-making processes with which nurses and physicians are faced in a neonatal unit. Which assessments underlie decisions about whether to start, continue or stop medical treatment of very sick premature babies? A descriptive study design, including 120 hours of field observations and 22 qualitative in-depth interviews with doctors and nurses, was chosen. Strauss and Glaser's comparative method was used to analyse the field observations and interviews. The findings indicate that life-and-death decisions are somewhat ambivalent; experience does not always make them easier. In situations of ambiguity, decisions also seem to be based upon the vitality of the babies concerned.