This paper has two objectives, first to review the relevant literature concerning the social importance of severity of pre-treatment condition, and second to present the results of a new analysis of the relationship between social value, individual assessment of health improvement and the severity of illness. The present study differs methodologically from others reported in the literature. The underlying hypothesis is that members of the public have an aversion to patients being in a severe health state irrespective of the reason for their being there, and that this aversion will affect the social valuation of a health program after taking account of the magnitude of the health improvement. This effect will be observable in a program which (compared to another) takes a person out of a severe health state--the usual case discussed in the literature--or in a program which (compared to another) leaves a person in a severe health state. The present study tests this second implication of the hypothesis. We present data consistent with the view that after taking account of health improvement, health programs are preferred which do not leave people in severe health states. Alternative explanations are considered and particularly the possibility that data reflect a social preference for individuals achieving their health potential. Both explanations imply the need to reconsider the rules for prioritizing programs. In this analysis, Person Trade-Off (PTO) scores are used to measure social preferences ('value' or 'social utility') and Time Trade-Off (TTO) scores are used to measure individual assessments of health improvement and initial severity. Econometric results suggest that severity is highly significant and may more than double the index of social value of a health service.