The influence of various factors on the activity of chloroperoxidase from Serratia marcescens was investigated. The enzyme is active only in acetate-containing buffers within the pH range 4.2-5.8. F-, Cu2+, [Fe(CN)6]4+, and [Fe(CN)6]3+ inhibit the enzyme. The chloroperoxidase is thermostable and resistant to the effect of lower alcohols.