Many Italian soils over which fire has passed are intensely eroded. To clarify the effect of fire on some factors associated with the soil erodibility, such as soil organic matter content, aggregate stability, and hydrophobic and cementing substances, we performed an experimental burning in a selected watershed characterized by surface layers of soil that repel water slightly. After the fire had passed, we noted a decrease in soil organic matter content in the upper soil layers, connected with the disappearance of the resistance to wetting and with the lowering of the aggregate stability. The upper part of the underlying B horizons showed an accumulation of organic matter and an increase in aggregate stability. Contrary to previous findings, no evidence for soil hydrophobicity was detected, but the discrepancy may be explained by the fine texture of the soil tested. The deeper horizons were practically unaffected by the fire.