The NHS internal market, introduced in an atmosphere of controversy, c
ontinues to generate much disagreement. This article examines the evid
ence on the impact of this policy with regard to a range of criteria,
including efficiency, accountability, effective planning and co-ordina
tion, patient choice and service quality, equity, and the culture of t
he NHS. It explores the different ways in which this evidence is perce
ived and seeks to make explicit the assumptions and biases of those in
volved in the debate about the reforms. The article also examines the
policy process behind the reforms and the extent to which it has added
to the problems of evaluation. By way of conclusion, the implications
for future health care reform are considered and a number of procedur
al changes suggested.