Contrary to reports in the literature, no correlation was found between the peroxidase activity of five soils or the numbers of peroxidase‐producing microorganisms and the abilities of the soils to condense 3,4‐dichloroaniline (DCA) derived from the hydrolysis of N‐(3,4‐dichlorophenyl) propionamide (propanil) to 3,3′,4,4′‐tetrachloroazobenzene (TCAB). Amending the soils with an energy source increased the production of peroxidase extractable from the soil but decreased the amount of TCAB formed. It has been reported that a peroxidase‐producing fungus isolated from soil was capable of converting DCA to TCAB. However, peroxidase isolated directly from a soil of this study was incapable of converting DCA to TCAB. Apparently not all soil peroxidases catalyze the conversion.