Objective.To develop and test a method for standardized calibrationof pulse oximeters. Methods.A novel pulse oximeter calibrationtechnique capable of simulating the behavior of real patients is discussed.It is based on an artificial finger with a variable spectral-resolved lightattenuator in conjunction with an extensive clinical database of time-resolvedoptical transmission spectra of patients fingers in the wavelength range600–1000 nm. The arterial oxygen saturation of the patients at the timeof recording was derived by analyzing a corresponding blood sample with aCO-oximeter. These spectra are used to compute the modulation of the lightattenuator which is attached to the artificial finger. This calibration methodwas tested by arbitrarily playing back recorded spectra to pulse oximeters andcomparing their display to the value they displayed when the spectra wererecorded. Results.We were able to demonstrate that the calibratorcould generate physiological signals which are accepted by a pulse oximeter.We also present some experience of playing back recorded patient spectra. Themean difference between the original reading of the pulse oximeters and thedisplay when attached to the calibrator is 1.2 saturation points (displayedoxygen saturation SpO2) with a standard deviation of 1.9 saturationpoints. Conclusions.The tests have shown the capabilities of aspectral light modulator for use as a possible calibration standard for pulseoximeters. If some improvements of the current prototype can be achieved weconclude from the experience with the device that this novel concept for thecalibration of pulse oximeters is feasible and that it could become animportant tool for assessing the performance of pulse oximeters.