Abstract: In a method and an apparatus for measuring the superficial blood flow in tissue, a section of the tissue is irradiated with monochromatic light from a laser source. Light scattered by moving blood cells and adjacent stationary structure within a part of the irradiated section is collected and passed to a photo-detector arrangement, which produces an output signal containing fluctuating signal components, a Doppler signal, deriving from interference between light components having differing frequencies due to having been scattered by moving blood cells and thereby subject to frequency shifts. The Doppler signal contains information concerning the number of blood cells present and the velocity at which they move. By means of a signal processor, there is derived from the Doppler signal a signal which is linearly related to the blood flow expressed as the product of the number of blood cells and their average velocity of movement, and a signal which is linearly related to the number of blood cells present.