Historically, the origins of CBA lie in investmentappraisal rather than policy appraisal, but in recentyears it has come to be used in the European contextmore in the policy context. CBA is widely practised.Why then does it remain so controversial, andespecially so in the context of the environment? Thisarticle outlines the use made of CBA in UK environ-mental policy and offers some explanations for thecontinuing controversies. But, while the debatescontinue, they should not be construed as meaningthat CBA is not widely used in British government.CBA has entrenched itself in policy appraisal farmore than ever before in UK history in the sensethat more CBA-type appraisals are conducted.However, there remains a gap between conduct-ing CBA and CBA affecting actual policy decisions.The reasons for this lack of correspondence be-tween practice and influence are explored