Budgetary restraints have been used to limit the freedom of medical pr
escription. This paper proposes a simple approach to the evaluation of
costs and benefits. First the efficacy of a new approach is defined a
nd compared with the best care with existing means. The incremental ga
in is then compared with the true cost of both procedures. The innovat
ion should be adopted only where the gain is high and the cost low (or
at least only minimally increased). In cases of debatable gain and co
sts, detailed cost-benefit analysis and quality of life studies are ne
eded. We conclude that at present, 5-HT3 receptor antagonists should o
nly be used to control the acute phase of emesis.