The lymph flow diagnostics in microvessels of rat mesentery were performed using light biomicroscopy, speckle- interferometry and spectroscopy. By light microscopy method we have got the dynamic of microvessels images in real time and registered phasic contractions and valve function of lymphatics, lymph and blood flow. The mean velocity of lymph flow was the highest at the moderate number of lymphocytes in flow. We had found the close links between phasic contractions, valve activity and lymph flow intensity. The high-resolution speckle-microscopy quickly gives much information about average lymph flow velocity, but only the relative value of velocity can be estimated. The phasic contractions cause the changes of the speckle signals and led to the modification of lymph flow in microvessels. The reflectance spectra characterize functional state of lymphatics and lymph flow in microvessels.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.