Chemodenitrification is of importance in both soils and the treatment of some types of wastewater. During model experiments, the impact of various conditions, such as pH and especially artificial humic matter and oxygen on this process was studied to build up kinetic models. The chemodenitrification rate decreased due to the ongoing autoxidation/polymerization of hydroquinone to artificial humic matter from 11.02 mug (L h)(-1) after 7 days autoxidation to 5.38 mug (L h)(-1) after 14 days at pH 4 under aerobic conditions and an initial nitrite concentration of 250 mug L-1. At the same pH, with the same nitrite concentration, and in the presence of Roth humic matter (2 mg L-1) under aerobic conditions, the chemodenitrification rate was 0.73 mug (L h)(-1), whereas under anaerobic conditions it was considerably higher (2.88 mug (L h)(-1)). In another model experiment, it was shown that the amount of nitrite incorporated into the artificial humic matter was less then 1%. Further, it was found that the main reaction product of chemodenitrification is NO.