Abstract: The invention is directed to an antimicrobial composition obtainable by reacting in a first step at least one polyiso-cyanate A with at least one binder component B with at least two isocyanatereactive groups and at least one isocyanatereactive alkoxysilane C thus obtaining a polyurethane and subsequently hydrolysing the siloxy groups in the polyurethane in a second step in the presence of an antimicrobial agent Z which has a siloxy moiety and condensing the hydrolized siloxy groups resulting in the formation of a silica network covalently linked to a polyurethane and to the rest of the antimicrobial agent Z and the use of this composition as antimicrobial coating especially for interior applications.