Patient management requires accurate blood pressure measurement, but there is concern about the accuracy of the equipment. Makes and types of sphygmomanometers and sizes of their associated cuffs used in hospital wards and outpatient departments were recorded and calibration checked. Half the sphygmomanometers were oscillometric, 32% aneroid and 18% mercury. There were faults in 30% of the aneroid devices and 32% of the mercury devices, mostly of cuffs, hoses and connectors. Of the aneroid devices 18% had calibration errors (mostly of only 4 mmHg at pressures above 200 mmHg). Nearly 90% of the aneroid devices had only one cuff size available, suggesting that miss-cuffing might be a serious cause of inaccurate blood pressure measurements. Many oscillometric devices had no evidence of compliance with validation standards. Sphygmomanometers and their cuffs and hoses should be regularly checked. Clinical staff can carry out many of the checks.