A new optical method for reduction of local tissue hypoxia is proposed. It is shown that this method of phototherapy allows the control of a local oxygen concentration in tissue. Different aspects of biomedical application of this phenomenon are discussed. The results of in vivo experimental investigation of the laser-induced photodissociation of oxyhemoglobin in cutaneous blood vessels and its role in tissue oxygenation are presented. The rates of oxygen saturation SpO2 in blood and their dependence on the wavelength of the transcutaneous laser irradiation have been experimentally measured.