Laser-Doppler flowmetry is a new method of the continuous and noninvasive measuring of the tissue blood flow, utilizing the Doppler shift of laser light as the information carrier. The method has already proved its potential usefulness in the clinical assessment of blood flow within disciplines such as dermatology, plastic surgery, and gastrointestinal surgery. In experimental medicine, laser-Doppler flowmetry has been used in the study of spontaneous rhythmical variations as well as in the study of spatial and temporal fluctuations in human skin blood flow. The method has facilitated further investigations of the nature of blood flow in a variety of tissue types. The method is rapidly spreading to many new applications in microvascular blood flow measurements. Several commercial laser Doppler instruments are available. This review article is a presentation of the state of the art of laser-Doppler flowmetry including theory, technology, and applications.