Recycled irrigation water is easily contaminated with plant pathogens and algae, therefore water must be sanitized prior to recirculation. Chlorine dioxide (ClO2), a common disinfectant used to treat municipal water and postharvest dump tanks, has been proposed as a disinfectant for recirculated irrigation systems. Little prior research has been performed to determine if this chemical is appropriate to use in irrigation on greenhouse specialty crops. The objective of this study was to determine the effects of ClO2 on the vigor of bell pepper plants at different concentrations (0, 10 20, and 40 ppm) and in two different soilless medias (perlite and pine bark). Plants were transplanted in the University of Florida Protected Agriculture Project greenhouse on 5-Nov.