Abstract: Arrangement for determining the oxygen saturation in human blood vessels and organs with a measurement sensor with at least two light sources of different wavelengths--preferably wavelengths of 660 nm and 940 nm--and with at least one receiver which receives the light transmitted and reflected from the oxygen particles which are bonded with the hemoglobin in the irradiated vessel or organ and transmits it as an electrical signal to a pulsoximeter for evaluation of the measurement results and readout on a display device. An additional measurement sensor is associated with the measurement sensor for locating a blood vessel or organ to be selected and the two measurement sensors are designed such that they can be handled together as a constructional unit.