The mechanisms of oxidation and reduction in Fenton's reagent were investigated using 1-hexanol and carbon tetrachloride (CT). Degradation of these compounds was investigated using different concentrations of hydrogen peroxide (2.94 mM ~ 1470 mM) at 1 mM concentration of ferric sulfate by varying pH from 3 to 12. The results showed that as pH was increased from 3 to 5, 7, 9, and 12, the degradation of 1-hexanol decreased significantly. Within 30 min (with 1470 mM of H2O2) of reaction time, decomposition of 1-hexanol was 99.9% at pH 3 ; however, only 5% was observed at pH 12. Carbon tetrachloride degradation showed different result; with 1470 mM of H2O2, 95% of initial CT concentration was decomposed at pH 3, but only 70% decomposed at pH 5. When pH was raised to 12, CT degradation reached up to 95% of the initial concentration. Furthermore, competition reactions were conducted at pH 3 and pH 9 to verify the formation of hydroxyl radical and reductants in Fenton's reagent. It was concluded that hydroxyl radical was the primary oxidant for the degradation of 1-hexanol, whereas in the degradation of CT, not the hydroxyl radical, but the reductants, superoxide radical and hydroperoxide anion were involved. This study indicates that Fenton reaction is a co-existing process of oxidative-reductive reaction.