The reduced thiols content (RSH) is one of the biochemical parameters of latex diagnosis (LD) in rubber trees (Hevea brasiliensis Muell. Arg.) (Will. ex A. Juss) associated with the incidence of tapping panel dryness (TPD). However, RSH is difficult to interpret due to the influence of the environment and calls for a comprehensive study of antioxidant dynamics, in different stress types and levels. This study was the first work on combined agronomic and physiological parameters related to latex production, latex diagnosis, antioxidants, and cofactors of H. brasiliensis latex in relation to harvesting stress (tapping and stimulation) as well as occurrence of TPD. The research aims to 1. observe the variation of antioxidant content in latex of rubber clones, 2. study the evolution of RSH content in response to different stress of tapping, ethephon stimulation, and TPD occurrence, 3. understand the RSH regulation under different stress types and duration, 4. Identify the better way to interpret RSH value in relation with harvesting stress and TPD occurrence, and 5. Examine the ratio of reduction to oxidised form of antioxidants as the estimator of stress level in Hevea brasiliensis latex. Three field trials were established to study.