Soil erosion processes are affected by the erodibility of the soil and by the erosivity of rain. Aggregate stability is commonly considered to be the most signifi cant soil physical property that determines soil erodibility. Barthès and Roose (2002), among others, proved that topsoil aggregate stability is closely and negatively related to soil susceptibility to runoff and soil loss. Both aggregate stability and soil erodibility are commonly considered to be constant properties, without taking into account the influence of time-dependent parameters, such as the antecedent soil water content θa, which is the soil water content before the rainfall (Le Bissonnais et al., 1995). While the effects of rain characteristics and of constant soil properties such as texture and organic matter content on soil erosion processes are well documented (e.g., Wischmeier et al., 1971; Morgan, 2005), the effects of θa on aggregate breakdown, seal formation, runoff production, and subsequent soil loss are still open for debate and opposing effects have been reported (e.g., Kemper and Rosenau,1984; Luk, 1985; Kemper et al., 1987; Bullock et al., 1988;Truman et al., 1990; Bajracharya and Lal, 1992; Le Bissonnais and Singer, 1992; Reichert and Norton, 1994; Le Bissonnais etal., 1995; Rejman et al., 2001; Lado et al., 2004).