Regulation of cellular redox balances is important for the homeostasis of human health. Thus, many important human diseases, such as inflammation, diabetes, glaucoma, cancers, ischemia and neurodegenerative diseases, have been investigated in the field of reactive oxygen species (ROS) and oxidative stress. To overcome the harmful effect of oxidative stress and ROS, one can directly eliminate them by medical gases such as carbon monoxide (CO), hydrogen sulphide (H(2)S), and molecular hydrogen (H(2)), or one can induce ROS-resistant proteins and antioxidant enzymes to antagonize oxidative stresses. This article reviews the molecular mechanisms how these medical gasses work as antioxidants, and how ROS resistant proteins are produced in the physiological context. Targeted therapeutic modalities to scavenge or prevent ROS might be applied in the prevention and treatment of ROS-related diseases in the near future.