Nanoparticles containing the fungicides tebuconazole or chlorothalonil were prepared with median diameters of similar to 100-250 nm. The nanoparticle matrices were polyvinylpyridine (PVP), copolymers of PVP and styrene (PVP-co-St), and blends of PVP and hyperbranched polyesters (HBPs). The isolated nanoparticles were resuspended in water to yield suspensions able to deliver 0.1, 0.2, 0.4, and 0.8 kg fungicide/m(3) of wood. Southern yellow pine (SYP) was treated with these suspensions using conventional vacuum-pressure treatments. Less concentrated suspensions delivered the nanoparticles quantitatively into the SYP while suspensions capable of delivering up to 0.8 kg of the fungicide (the active ingredient or AI) per cubic meter of SYP delivered 0.4-0.7 kg AI/m(3), depending on the nanoparticle matrix. The SYP lost less than 5% of its mass after 55 days of exposure to Gloeophyllum trabeum when the tebuconazole content in the SYP reached 0.2 kg/m(3), and the matrix identity had little effect on the results. The SYP lost between 3 and 6% of its mass after 55 days of exposure to G. trabeum when the AI was chlorothalonil at a level of similar to0.6 kg AI/m(3) of wood and was introduced into SYP in nanoparticles with a PVP/HBP matrix, but it lost similar to11% of its mass at the same AI levels when the nanoparticle matrix was PVP.