A hybrid coating is prepared on a glass surface by a sol-get process using tetraethoxysilane (TEOS) and Q(4)N(+)-Si(OR)(3). Transparent coatings with smooth surfaces were investigated against both Gram-positive (Escherichia coli) and Gram-negative bacteria (Staphylococcus aureus). A rapid decrease of the Count for both strains was observed within 72 h. A significant correlation has been observed between the concentration of Q(4)N(+)-Si(OR)s and the antibacterial activity which has been thoroughly investigated.