The influence of coprecipitated hexagonal barium ferrite BaFe12O19 phase on the cure characteristics and dynamic properties of natural rubber-ferrite composites has been Studied as a function of ferrite loading up to 220 phr (part per hundred part of rubber). Unusual characteristics of coprecipitated ferrite particles were discovered by scanning electron microscope. The results show that scorch time t(10) and cure time t(90) decrease dramatically with increasing ferrite content LIP to critical ferrite loading. After 160 phr, t(90) increases sharply with increasing ferrite content, in contrast to saturation of t(10). Minimum torque recorded normal behaviour at low ferrite loading, whereas it decreases with increasing ferrite content at high ferrite loading because of dilution effects. The storage modulus E' and loss modulus E '' decrease with increasing temperature. The loss tangents (tan delta) of the composites are greater than those of the pure rubber. Linear viscoelastic behavior was observed as a result of the homogeneity and compatibility of the composites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3294-3299, 2009