Given the variability of blood pressure, it is often difficult to make a diagnosis of hypertension or to evaluate the effect of treatment on the basis of single blood pressure readings in the office. To obtain multiple measurements one can either turn to ambulatory blood pressure monitoring or have the patient take his or her own pressure. Both approaches require the availability of reliable, validated devices. Currently, only some instruments which measure blood pressure oscillometrically at the upper arm can be recommended for self-measurements. Studies are in progress to assess the prognostic significance of self-measured blood pressure data.