A peroxidase has been isolated from pooled specimens of human cervical mucus. Investigation of substrate and inhibitor specificity, pH optimum, chromatography on Sephadex G-200, disc electrophoresis, ultraviolet absorption spectrum and the effects of temperature and ionic strength variation are described. A study of the steady-state kinetics is reported using hydrogen peroxide and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) as substrates and a catalytic mechanism is proposed.