The effect of a number of environmental parameters (pH, temperature, carbon and nitrogen ratio of nutrient) on the production of extra- cellular peroxidase enzymes by Streptomyces avermitilis UAH30 was examined. Maximum specific peroxidase activity (0.12 U/mg of protein) was obtained after 72 hours of 1 incubation at 45 degrees C in a minimal salt medium (pH 7.5) containing 0.6% (w/v) yeast extract and 0.6% (w/v) xylan corresponding to a C:N ratio of 4 to 1. A study of the effect of incubation on peroxidase activity showed that the enzyme was stable and active for at least one hour after incubation at 50 degrees C while at higher temperatures the stability and activity of the peroxidase was reduced such that at 60 degrees C the peroxidase activity has a half life of 20 min while at 80 degrees C the half life was reduced to 5 min. The activation energy for deactivation as a result of thermal denaturation of the enzyme was calculated to be 80 +/- 7 kJ/mol. The optimum pH for the activity occurred between a pH range of 6.5-8.5 with pKa(1) and pKa(2) of 5.1 +/- 0.1 and 9.7 +/- 0.1, respectively. The K-m and V-max for the peroxidase activity were determined to be 1.45 mM and 0.31 unit per mg protein respectively using 2,4-dicholorophenol (2,4-DCP) as a substrate. Characterization of the peroxidase activity revealed activity against L,3-4 dihydroxyphenylalanine and guaiacol, while no inhibition of peroxidase activity could be detected with the haem inhibitors such as potassium cyanide and sodium azide, suggesting the lack of haem component in the tertiary structure. Aspects of using the crude peroxidase preparation in the pulp and paper industry are discussed.