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The effect of PAM application rate on critical shear stress and erosion was determined for 7 different soils, with a wide range of textural and chemical properties. At least four PAM application rates were tested on each of the soils, ranging from 0.1 to 80 kg ha-1. Flow rates ranging from 4 to 56 L min-1 were introduced to a 4.5 m long, 15 cm wide rill set to a 10% slope. Two procedures were used to estimate critical shear and rill erodibility using SAS statistical software, a simple regression and a weighted regression. The criterion for model selection and the regression method had a large impact on estimates of critical shear and erodibility. Critical shear for PAM treated soils was related to initial aggregate size distribution. Less PAM was required to increase the critical shear stress for those soils having a smaller initial aggregate size distribution. The smaller distance between aggregates for finer aggregated soils is thought to enhance inter-aggregate strength at the soil surface more so than for more coarsely aggregated soils.