The phenol precipitation and dye bleaching capabilities of phthalic anhydride-modified horseradish peroxidase C (PA-HRP) were compared with those of native HRP C and ethylene glycol-bis(succinic acid N-hydroxysuccinimide ester)-modified HRP (EG-HRP) reported previously. Removal efficiency (percentage of phenol removed from solution under experimental conditions) was determined for native HRP and both modified forms. Removal efficiencies at 37 degrees C were very similar, with >95% removal in each case. Removal efficiencies were less at 70 degrees C overall (range 25-45%) but PA-and EG-HRP removed up to 50% more phenol than native HRP. The three HRP forms showed similar dye bleaching performance at 37 degrees C in the presence of H2O2 and accelerators (up to 86% colour removal). FA-and EG-HRP showed slightly greater bleaching abilities at 65 degrees C than native HRP for some of the dye/accelerator combinations tested. Modified HRPs performed better in 40% (v/v) mixtures of dioxane or dimethylformamide.