To propose ozone microbubbles (O 3MB) as a new disinfection method for the nutrient solution used in hydroponic culture, we investigated the disinfectant effect of O 3MB against Fusarium oxysporum f. sp. melonis and Pectobacterium carotovorum subsp. carotovorum, which are a pathogenic fungus and bacterium that infect plants via the roots, and the effect of O 3MB on the composition of nutrient solution and plant growth. Since O 3MB dissolves more efficiently in solution than O 3 millibubbles (O 3MM) over a short period, it is regarded to be highly effective as a disinfectant against F. oxysporum f. sp. melonis and P. carotovorum subsp. carotovorum. Disinfectant effect was observed when O 3MB treatment was performed once or twice a week at approximately 0.2 ppm of dissolved O 3 in a nutrient solution kept at 20°C. Concentrations of Mn and Fe in the nutrient solution dropped because of O 3MB treatment; however, no effect was observed on other fertilizer components. Furthermore, O 3MB had no adverse effects on the growth of lettuce that was cultivated in this study. While it is necessary to devise a way to counteract the deficiency of Mn and Fe in nutrient solution depending on the cultivated plant, this study suggests that O 3MB can be used as a new disinfectant technique for the nutrient solution used in hydroponic culture. © 2012 ASABE ISSN 1934-2799.