Peroxidases are an enzyme family that displays a wide range of forms, functions, and distribution in the plant kingdom. Peroxidase extracted from horseradish is one of a few enzymes that had been widely used in industrial and clinical research. Horseradish peroxidase (HRP, EC 1.11.1.7, donor: hydrogen-peroxide oxidoreductase) has been used to estimate the levels of other enzymes, in immunoassay, bio-bleaching processes, and in lignin degradation for fuel production. Despite its extensive use, little is known about HRP distribution in horseradish plants. Four commercial horseradish cultivars (IL-647, IL-1069, IL-1573, and IL-1590) were evaluated for HRP activity in the main root, lateral roots, leaves, and leaf blades. HRP activity was highest in the main root followed by lateral roots. However, only a trace amount of HRP activity was detected in leaf blade and leaf petiole. IL-1573 has the highest HRP activity, while IL-647 has the lowest activity. Site of HRP synthesis and its distribution during horseradish plant growth and development will be described.