An antimicrobial composition comprising an antimicrobically effective amount of a fine particle dispersion containing a biocidally, cationcally active surfactant quaternary ammonium compound in an aqueous media, wherein the dispersion of a cationic polymer contains biocidal cationically surfactant quaternary organic ammonium compounds of the formula I and/or II ##STR2## in which R.sub.1 =(C.sub.8 -C.sub.18)-alkyl or -alkenyl,
- R.sub.2 =(C.sub.8 -C.sub.18)-alkyl or -alkenyl, aryl or (C.sub.7 -C.sub.18)-aralkyl, in which the aromatic rings are unsubstituted or substituted with at least one member of the group consisting of chlorine and bromine
- R.sub.3 =(C.sub.1 -C.sub.4)-alkyl or the radical --(CH.sub.2 --CHR.sup.4 O).sub.n --R.sup.5, in which n denotes a number from 1 to 20 and R.sup.4 and R.sup.5, which can be identical or different, denote H and/or (C.sub.1 -C.sub.4)-alkyl, and
- A=an anion of an organic or inorganic acid.