The in vitro antioxidant properties of squeezed juice from black radish root were investigated by spectrophotometry and luminometry. The sample exhibited strong hydrogen-donating ability, reducing power, copper(II)-chelating property and showed a radical scavenging effect in a H2O2/˙OH-luminol system that points to significant participation in an antioxidant process. According to the HPLC analyses the main active compounds in the juice are not the glucosinolates but probably their degradation products formed by myrosinase hydrolysis. Since a significant amount of polyphenols could be detected in the juice, these compounds could be responsible for the beneficial effect. Copyright © 1998 John Wiley & Sons, Ltd.