The flame retardancy of synthesized melamine polyphosphate (MPP) in combination with starch (ST) and different metallic hydroxides was investigated in low density polyethylene (LDPE) by limiting oxygen index (LOI) and vertical burning test. The results indicated that the LOI value of composite comprising Al(OH)(3)(ATH) was higher than those of composites at the same additive loading with Mg(OH)(2)(MH) or Fe(OH)(3)(FH), which increased from 22 to 27%. And the composite comprising ATH passed V1 rating without causing molten drops. In addition, thermostability and morphology were characterized by differential scanning calorimeter (DSC), thermogravimetry (TG), derivative thermogravimetry (DTG), and scanning electron microscope (SEM). The results demonstrated that the crystallization of the composites remained unaffected after the incorporation of metallic hydroxide. The thermal degradation behavior of LDPE composites and the morphology of residual charred layer were changed. It also can be concluded that there was a synergy between certain metallic hydroxide and MPP after analyzing the residual charred layer using X-ray diffraction (XRD). (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3263-3269, 2011