Oxygen saturation of arterial blood (SpO2) is a measure of how much oxygen the arterial blood is carrying as a percentage of the maximum it could carry. Pulse oximeters estimate oxygen saturation utilizing a suitable sensor and a calibration curve obtained through empirical curve fitting. Thus the accuracy of the present day pulse oximeters is affected by sensor and patient dependent parameters. The book presents basics of pulse oximetry and innovative methods for estimation of SpO2 that are free of interference due to sensor and patient dependent parameters. The book should be of interest to biomedical engineers, healthcare providers. This also could serve to bridge the gap between industrial medical instrumentation application to pulse oximetry and academic research.