A method of estimating oxygen saturation includes illuminating a target site with light of three different wavelengths, for example green, red and infrared, and detecting light returned from the site at each of the wavelengths. The method distinguishes between cardiac pulsatility and nonpulsatility based on a parameter of the return light of the shortest wavelength. The method formulates an estimate of oxygen saturation as a function of a parameter of the light of the two longer wavelengths taken at both a period of pulsatility and at a period of nonpulsatility. An oximeter adapted to carry out the method is also disclosed. Aspects of the method and oximeter may be used to estimate other physiological parameters.