A new family of amine- and ammonium-terminated carbosilane dendrimers of the type Gn-[Si(CH2)3N(Et)CH2CH2NMe2]x and Gn-{[Si(CH2)(3)N+R(Et)CH2CH2N+RMe2]x(X-)y} (where n = 1, 2 and 3; R = H, X = Cl; R = Me, X = I) respectively has been synthesized by hydrosilylation of N,N-dimethyl-N'-allyl-N'-ethyl-ethylenediamine, [(CH2=CH-CH2)(Et)N(CH2)2NMe2] with the corresponding hydride-terminated dendrimers and subsequent quaternization with HCl or MeI. Quaternized dendrimers are soluble and stable in water or other protic solvents for long time periods. The antibacterial properties of the quaternary ammonium functionalized dendrimers have been evaluated showing that they act as potent biocides in which the multivalency along with the biopermeability of the carbosilane dendritic skeleton play an important role in the antibactericidal activity of these compounds.