We compared blood pressure recordings made with the A&D UA-751 semi-automated cuff-oscillometric sphygmomanometer (A&D Co. Ltd, Tokyo, Japan) and with a conventional Hawksley random-zero mercury sphygmomanometer (Hawksley and Sons Ltd, Lancing, UK). Simultaneous single-arm recordings were obtained in duplicate with both devices in 200 subjects having blood pressure in the ranges 92-221/51-121 mmHg. The measurements obtained by three observers using the Hawksley sphygmomanometer were compared with recordings from two A&D UA-751 devices. In most cases, there was an acceptable level of agreement between the results, according to the criteria suggested by the Association for the Advancement of Medical Instrumentation (range of differences systolic: mean - 0.9 to 1.4 mmHg, s.d. 4.6-9.8 mmHg; diastolic: mean - 0.6 to 1.3 mmHg, s.d. 2.9-5.1 mmHg), although there were sizeable discrepancies in individual subjects. Thus the A&D UA-751 device appears to be an acceptable alternative to a conventional sphygmomanometer; it should be suitable for routine clinical and limited research use, including intermittent home blood pressure recording.