Clinical practice guidelines are expanding their scope of authority from clinical decision making
to collective policy making, and promise to gain ground as resource allocation tools in coming
years. A close examination of how guidelines approach patient selection criteria offers insight
into their ethical implications when used as resource allocation or rationing instruments. The
purposes of this paper are: a) to examine the structure of allocative reasoning found in clinical
guidelines; b) to identify the ethical principles implied and compare how guidelines enact these
principles with how explicit systems-level rationing exercises and health policy analyses have
approached them; and c) to offer some preliminary suggestions for how these ethical issues
might be addressed in the process of guideline development. The resulting framework can be
used by guideline developers and users to understand and address some of the ethical issues
raised by guidelines for the use of scarce technologies.