In this work, the effect of composition, particle size and particle size ratio on the tensile properties of well-characterized hard/soft latex blends was investigated. Four blends of hard/soft latices, with varying particle sizes (either small or large), and volume fractions of 100/0, 80/20, 60/40, 50/50, 40/60, 20/80 and 0/100 were studied. The stress at break increased and the strain at break decreased as the amount of hard particles in the blend increased. A simple model, introduced by Pukanszky for filled polymers and polymer blends, proved to be a very useful tool for evaluating the tensile properties of the latex blends. Parameter B of the model could be related to the specific surface of the dispersed hard particles and the particle size ratio. Increasing the specific surface of the dispersed hard particles resulted in an increase in parameter B. The influence of particle size ratio on parameter B was shown to depend on the formation of aggregates.