Information about the activity of the autonomic nervous system can be derived by analysis of key physiological signals on a beat-to-beat basis. However, due the large amount of data and complex mathematical processing involved, analysis by hand is prohibitive. The solution developed facilitates this procedure by performing the entire processing on a dedicated stand-alone PC-based instrument incorporating existing medical equipment, a data acquisition board and a computer program to acquire and process the physiological signals. The automated virtual instrument was written using LabVIEW as the main platform. The techniques implemented include impedance cardiography, time and frequency domain analysis, invasive and non-invasive baroreflex sensitivity assessment, and forearm blood flow measurements. The system was designed to study patients suffering vasovagal blackouts where the changes that occur in the heart and circulation during an attack could increase our understanding of the physiological processes which underlie their blackouts.