The quantity and toxicity of soluble products resulting from enzyme catalyzed polymerization and precipitation of aqueous phenol were investigated. An accumulation of toxic, soluble products occurred during the enzymatic reaction for treatments conducted with peroxidases originating from soybeans (SBP) and horseradish (HRP) at intermediate and high levels of phenol treatment. The quantity of residual products was slightly greater when treatment was accomplished with HRP instead of SEP. Greater quantities of soluble products were formed during the treatment of higher concentrations of phenol. However, the toxicity of treated solutions was independent of the initial phenol concentration when near complete removal of phenol was achieved. The use of polyethylene glycol as an additive to protect the enzyme resulted in an increase in the quantity of soluble products but did not have a significant effect on the residual toxicity of treated solutions.