Several readers reported to us an inconsistency between some illustrations in Eoin O'Brien and colleagues' ABC article on sphygmomanometry (21 April, pp 981-5) and what was said in a Clinical Review article by McAlister and Straus the previous week (14 April, pp 908-11). The ABC illustrations showed the diaphragm of the stethoscope being used, whereas McAlister and Straus, in their evidence based review of blood pressure measurement, said that the bell should be used (see “Guidelines” box in their article). The readers wondered which is the correct method (bell or diaphragm). It may come down to differences in practice between North America and the United Kingdom. O'Brien and colleagues told us that the British Hypertension Society's recommendations on blood pressure measurement advocate using the diaphragm rather than the bell, as no evidence exists to support using the bell in modern stethoscopes. McAlister and Straus said that evidence shows minimal or no difference between the bell and the diaphragm and that their article followed the guidelines of the American Society of Hypertension and the American Heart Association. See www.bmj.com/cgi/eletters/322/7292/981 for the authors' full responses.