Natural rubber composites were prepared by the incorporation of palm ash at different loadings into a natural rubber matrix with a laboratory-size two-roll milt (160 x 320 mm(2)) maintained at 70 +/- 5 degrees C in accordance with the method described by ASTM D 3184-89. A coupling agent, maleated natural rubber (MANR), was used to improve the mechanical properties of the natural rubber composites. The results indicated that the scorch time and cure time decreased with increasing filler loading, whereas the maximum torque exhibited an increasing trend. Increasing the palm ash loading increased the tensile modulus, but the tensile strength, fatigue life, and elongation at break decreased. The rubber-filler interactions of the composites decreased with increasing filler loading. Scanning electron microscopy of the tensile fracture surfaces of the composites and rubber-filler interaction studies showed that the presence of MANR enhanced the interfacial interaction of the palm ash filler and natural rubber matrix. The presence of MANR also enhanced the tensile properties and fatigue life of palm-ash-filled natural rubber composites. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2867-2876, 2008