The invention relates to aqueous, fungicidal compositions and the use thereofin combating harmful micro organisms and particularly for protecting cellulose-containing materials, especially wood, from being attacked by micro organisms,particularly noxious fungi which can damage wood or cellulose. The inventiveactive substance compositions contain: a) at least one fungicidal organicactive substance having a degree of solubility in water of no more than 5 g/Iat 25 ~C/1013 mbar and b) a fine-particled polymer having an average particlesize (determined by dynamic light scattering) of no more than 300 nm, whereinthe polymer particles contain the active substance, wherein the polymer isconstructed from ethylenically unsaturated monomers M, comprising: - at least60 wt.- %, in relation to the total amount of monomers M, of at least oneneutral monoethylenically unsaturated monomer Ml having a degree of solubilityin water of no more than 30 g/I at 25 ~C and up 40 wt.- %, in relation to thetotal amount of monomers M, of one or several ethylenically unsaturatedMonomers M2 different from monomers MI.
