This paper describes an HPLC method to simultaneously determine methyl-parathion and phoxim in mixed formulation of methyl-parathion, phoxim and cypermethrin. A C8 column was used. The mobile phase was V(MeOH):V(H2O) = 70:30, Methyl-parathion and phoxim were monitored at 254 nm or 280 nm by UV detector. The average recoveries were 99.8% and 99.9% for methyl-parathion and phoxim respectively. The linearity of detector response vs concentration was calibrated in the concentration ranges from 0.1746 to 1.091 g/L for methyl-parathion and from 0.1927 to 1.205 g/L for phoxim.