Abstract: The present invention relates to a method for measuring blood flow in living tissue and a device for performing the method. The device comprises a laser and a photo sensor. The laser is arranged to illuminate (10) the tissue in such a way that a portion of the light beam, scattered by the tissue, re-enters the laser in order to obtain a self-mixing effect. The resulting light, that is registered (11) as an electric signal by the photo sensor, contains a speckle pattern that is depending on blood cell movement in the tissue. A Fourier transform is applied (12) to this signal and an exponential fit is applied (13) to the resulting frequency domain spectrum. Thereby parameters corresponding to the amount of blood cells and the average velocity of these cells may be obtained.