In this study the action of different doses of glucose solution on scattering properties of skin in vivo have been investigated. The application of glucose as hyperosmotic agent leads to the significant increasing of the tissue optical transmittance. There are dose dependent and time dependent effects of glucose on the skin reflectance. The good clearing of tissue is given after undercutaneous administration of 40 percent and 35 percent glucose solutions. The application of such doses of glucose allows one to visualize the small blood vessels in rat skin. The optimal interval of time for the clearing of rat skin is 15 minutes after injection. The method of clearing tissue is conventient, cheap and simple for The diagnostic of microcirculation of skin in vivo.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.