Silica powders consisting of small spherical particles (50-200 nm) have been obtained by the sol-gel method. A suspension of such particles in the Krebs-Hanseleit solution has been introduced into the coronary circulation of a beating perfused rat heart. The influence of the suspension on the heart muscle and the coronary vessels in the rat body has been histopathologically examined. The particles have not left the lumen of the vessels and have not caused any side effects. These observations suggest the possibility of using such silica particles as a carrier for selected drugs.