OBJECTIVE The focus of intraoperative monitoring is moving away from invasive monitoring. This has been attributed to procedure time, cost, and the known risks, which include carotid artery puncture, arrhythmia, pneumothorax, and infection. Until recently, the venous system's contribution to the circulatory system has been incorrectly identified as being insignificant. This article summarizes the unique characteristics of the peripheral venous system. RESULTS Numerous studies done in the last few years have paid attention to peripheral venous pressure and more specifically its pressure waveform. The popularity of, and further focus on, the field of photoplethysmography has described a strong venous component. Analysis of venous waveforms has indicated that, like arterial waveforms, they too exhibit respiratory variations and change in response to physiologic challenges. CONCLUSIONS The veins play a critical role in cardiovascular homeostasis; they do more than conduct blood to the heart. Considering the ease of measurement from a peripheral intravenous catheter, further study should be conducted to investigate the usefulness and limitations of such a minimally invasive and inexpensive monitoring device.