This paper reports the results of an investigation into the impact of the revaluation of fixed assets on the reported results of NHS ambulance services. It recalculates the accounting rate of return of individual trusts after removing revaluation adjustments and examines the published responses of trusts. The numerical analysis demonstrates that, in general, revaluation has depressed the stated rate of return in an inconsistent manner. Failure to meet the required rate of return may cause a trust to be subjected to additional monitoring and management reorganisation, while the trusts respond by explaining deviations in the accounting return measure by referring to revaluations and other technical adjustments. Management decisions made in response to the accounting measures may be sub-optimal in delivering health care but appropriate in achieving the desired accounting outcome.