The oxidation and reduction of metals in natural waters can affect their reactivity by controlling their redox speciation. The rates of redox processes of metals with reactive intermediates such as HO₂, H₂O₂, and O₂ can determine the form of a given metal in solution. This paper will review the recent kinetic measurements of redox reaction of metals in natural waters. The review will concentrate on how ionic interactions affect the rates. The metals considered are Cu(I) - Cu(Il), Fe(ll) - Fe(III) and Cr(III) - Cr(VI) in marine waters. Rate equations are given for these redox processes as a function of temperature, ionic strength, composition and pH.