We demonstrated that self-extinguishing polymer nanocomposites, which can pass the stringent UL 94 V0 standard, can be successfully prepared by combining modified organoclays with traditional flame retardant (FR) agents. Using secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM), we determined that the addition of modified clays, which can intercalate or exfoliate in the matrix, also improved the dispersion of the FR agents. Dynamic mechanical analysis (DMA) indicated that the clays increased the modulus of the polymer above Tg, which prevented dripping during burning. Cone calorimetry test showed that the nanocomposites with both FR and organoclay, had a lower peak heat release rate (PHRR) and average mass loss rate (MLR) than those with only clay or the FR agents. Extended X-ray absorption fine structure (EXAFS) data confirmed that no FR/clay interactions occurred in the solid phase, and that the synergistic effects were due to gas phase reactions. Since this mechanism is not specific, it opens the possibility of formulating self-extinguishing materials from a large class of polymers. 2006 Elsevier Ltd. All rights reserved.