To present an overview of the applicability of heart rate variability measurements in medicine.During a 4-year period all new papers concerning heart rate variability were collected. A selection of the most recent publications in the presented research area was used for this review.The amount of short- and long-term variability in heart rate reflects the vagal and sympathetic function of the autonomic nervous system, respectively. Therefore heart rate variability can be used as a monitoring tool in clinical conditions with altered autonomic nervous system function. In postinfarction and diabetic patients, low heart rate variability is associated with an increased risk for sudden cardiac death. A sympathovagal imbalance is also detectable with heart rate variability analysis in coronary artery disease and essential hypertension. Besides diabetic neuropathy, in many other neurologic disorders, such as brain damage, the Guillain-Barré syndrome, and uremic neuropathy, heart rate variability analysis can provide insight into which division of the autonomic nervous system is most affected. Heart rate variability can be influenced by various groups of drugs, but it can also shed light on the mode of action of drugs. The protective effect of cardiovascular drugs in postinfarction patients has been investigated.Heart rate variability analysis is easily applicable in adult medicine, but physiologic influences such as age must be considered. The most important application is the surveillance of postinfarction and diabetic patients to prevent sudden cardiac death. With heart rate variability analysis, individual therapy adjustments to achieve the most favorable sympathetic-parasympathetic balance might be possible in the future.