Photocatalytic oxidation process can be an effective method for the removal of toxic organic compounds from dilute aqueous solutions. Three toxic compounds, namely, dichlorvos (an insecticide), propoxur (an insecticide), and 2, 4-D (a herbicide), were used as the model compounds for the mineralization experiments. Total organic carbon measurements were used to measure the extent and the rate of the mineralization of these toxic chemicals. Additionally, ions such as chloride, phosphate and ammonia were also measured during the photomineralization reaction. Results show that the photocatalytic system is effective in mineralizing these pesticides. Both pH and the initial concentration of the organic compounds affect the mineralization reaction. The mineralization reaction is favored under an acid condition and increases with increasing initial organic concentration. The initial rate of the photomineralization reaction can be described by a Langmuir-Hinshelwood expression.