Self monitoring of blood pressure by hypertensive patients has been shown to be of value and is increasingly popular. However, the accuracy and ease of use of at least some of the equipment for home use is questionable. We tested 23 pairs of home blood pressure devices, using static methods, trained observers with volunteer subjects and hypertensive patients. Eleven (48%) of the 23 pairs of devices tested were found inconsistent with their duplicate and failed the standards for automated devices of the Association for the Advancement of Medical Instrumentation. Several of the devices, all sold for home use by lay people, contained no instructions whatsoever and even patients using those machines with instructions required further training in blood pressure measurement. While home blood pressure monitoring is useful in certain circumstances, care must be taken in the choice of device, and training is required for all devices.