The increased level of reactive oxygen species (ROS) in living organisms over 60 years ago was implicated in the development of diseases and aging (Harman, 1956; 1983). This book is a collective scientific monograph presenting several important aspects related to ROS role in human and animal pathologies. In 1985, German scientist Helmut Sies first denoted oxidative stress concept, which immediately attracted attention of researchers in diverse basic fields. Several discoveries substantially stimulated the interest to ROS as ones related to many diseases. They were descriptions of catalytic function of superoxide dismutase (erythrocuprein or hemocuprein) by McCord and Fridovich (1969) and role of superoxide anion in host defense against pathogens.
