The tensile failure of thin films prepared from polyolefin elastomer dispersions was studied. The elastomer dispersions were composed of copolymers of ethylene and 1-octene, dispersed in water at solids concentrations of approximately 50%. The density of the polyolefin resins ranged from 0.855 to 0.885 g cm(-3). The melt index of the resins ranged between 0.5 and 5.0 g 10 min(-1). As expected, the tensile strength of neat polyolefin films was found to be a strong function of the density and a weak function of the melt index. Dispersion blends were prepared from neat polyolefin dispersions. The film tensile properties were measured as a function of the blend ratio and the particle-size ratio. The blend ratio was found to be the dominant factor. it was found that blending the dispersions had an antagonistic effect on the tensile properties. The ultimate tensile strength of the blend film was lower than expected from the arithmetic mean behavior (based on the weight fraction) of the two constituent resins. A similar result was observed for the ultimate elongation, that is, blending of the two elastomers gave inferior behavior. The relationship between the experimental tensile properties and the blend ratio fit a quadratic function. A Monte Carlo simulation was used to model film failure in two dimensions. The two particle types were assumed to pack randomly and failure was forced to occur by the lowest-energy path. The simulated ultimate tensile strength was also found to be a quadratic function of the blend ratio, confirming the suitability of the model.