Expected and observed values for the prescription of vitamin B 12 in England and Wales.

as we know, no attempts to compare quantitatively the expected amount prescribed, on the basis of good clinical practice, with that actually prescribed. There are in general three reasons for this-ignorance of the prevalence of common diseases, the lack of specificity of particular drugs for particular diseases, and the lack of standardization of therapy. Such a study requires a drug which is practically specific for one condition whose prevalence is known, and the one which approximates most closely to this appears to be vitamin B12. We should like to stress that B12 was selected for these purely epidemiological considerations and with no malice aforethought. This paper describes an attempt to measure the expected and observed values for the prescription of B12 in England and Wales for the year 1966.