Tapping panel dryness (TPD) syndrome, generally considered as a stress-induced physiological disorder, is a consequence of abnormal exploitation in rubber (Hevea brasiliensis). Numerous studies in other crops have revealed that stress induced/enhances the formation of free radicals (FR) which gets moped up by its scavenging system. To study the status of free radicals and its scavenging system during occurrence of TPD, normal plants were subjected to to frequent tapping and stimulation treatment (10;ethephon), to accelerate the occurrence of the syndrome. A significant negative correlation was observed between FR in the bark and superoxide dismutase (SOD) in the lutoid with tapping. The study also revealed that the amount of FR in frequently tapped plants (where the wounding was excessive) was less than that of in the frequently tapped trees than in the stimulated ones. Interestingly however, at the 115th actual tapping, the occurrence of TPD was found to be higher in the stimulated samples than that of in the frequently tapped plants. The control plants showed no TPD syndrome in both cases. This implies that excess generation of active oxygen with defective defense mechanism (in terms of SOD) along with frequency of exploitation, sourcesink imbalance etc. may determine the yielding potential and the TPD incidence in rubber.