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The extension of viticulture on hill slopes in the Mediterranean basin might be responsible for a loss of organic carbon from the soil, as a result of increasing runoff and erosion. The loss of C makes soil aggregates less stable, which in turn increases erosion risk. We should use indicators of these risks and so be able to identify the most threatened areas. We first tested four widely used methods for determining aggregate stability for their ability to predict runoff and erosion; all include slaking and give indices such as rates of stable (> 200 mm) macro-aggregates (MA200) or mean weight diameter (MWD). We selected three Mediterranean vineyards characterized by brown calcareous soils and on which we had previously studied the effects of simulated rainfall. The tests were made on the soils from five farming situations, corresponding to 14 simulated rainfalls with an intensity of 60 mm hour ÿ1 . The two indices that best predict erosion are those resulting from the method of Le Bissonnais (MWD in its logarithmic form and MA200). Then, we analysed the relations between aggregate stability and soil properties on 68 soil samples from various locations within the three selected sites. A very significant correlation between the two indices of Le Bissonnais's method and soil organic carbon content was found and we propose a pedotransfer function linking these indices to soil characteristics. The results stress the need for farming practices that preserve the organic C in Mediterranean vineyard soils in order to reduce erosion risks. We believe that our findings might well apply to similar soils elsewhere in the world.Erodibilité des sols de vigre Méditerranéens: Mesure de la stabilité structurale et caractéristiques déterminantes des sols Résumé Le de´veloppement de la viticulture sur les sols en pente du bassin Me´diterrane´en pourrait entraıˆner une diminution de la teneur en C de ces sols et une aggravation du ruissellement et de l'e´rosion. La perte de C rend les agre´gats moins stables, ce qui augmente le risque d'e´rosion. Des indicateurs de ces risques sont ne´cessaires afin d'identifier les surfaces les plus menace´es. Nous avons dans un premier temps compareq uatre me´thodes diffe´rentes, couramment utilise´es pour mesurer la stabilite´structurale des sols afin d'e´valuer leur capacite´a`pre´dire le ruissellement et l'e´rosion; toutes mettent en jeu de l'e´clatement des agre´gats et produisent des indices tels que la proportion de macroagre´gats stables > 200 mm (MA200) ou le diame`tre moyen ponde´re´des agre´gats stables (MWD). Nous avons choisi trois vignobles me´diterrane´ens, caracte´rise´s par des sols bruns calcaires. Les tests de stabilite´structurale ont e´te´re´alise´s sur les sols de cinq sites cultive´s, correspondant a`14 simulations de pluie avec une intensite´de 60 mm heure ÿ1 . Nous avons trouve´des relations significatives entre la stabilite´structurale et le comportement lors d'une pluie simule´e, les deux meilleurs pre´dicteurs de l'e´rosion e´tant les indices MWD logarithmique et MA200 i...

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